Guide to the MetaCyc Database

Contents

    1  Introduction

    2  MetaCyc Overview
        2.1  Motivations
        2.2  Database Contents
        2.3  Query and Visualization
        2.4  The MetaCyc Data Universe
        2.5  Linking to MetaCyc
        2.6  Development
        2.7  Underlying Software

    3  Position of MetaCyc Within the BioCyc Collection

    4  MetaCyc Availability

    5  Release Frequency and History

    6  MetaCyc Curation
        6.1  Information Types Captured During the MetaCyc Curation Process
            6.1.1  Pathways
            6.1.2  Reactions
            6.1.3  Enzymes and Enzyme Complexes
            6.1.4  Genes
            6.1.5  Compounds

    7  Taxonomic Designations for Pathways

    8  Database Links

    9  Data Sources

    10  Comparison of MetaCyc to other Pathway Databases
        10.1  KEGG
        10.2  UM-BBD
        10.3  Reactome

    11  The MetaCyc Team
        11.1  Current Contributors
        11.2  MetaCyc Advisory Board
        11.3  Past Contributors

    12  Submitting Pathways for Incorporation into MetaCyc
        12.1  How to Ensure that You and Your Organization Receive the Appropriate Credit
        12.2  How to Send Pathways to MetaCyc

    13  MetaCyc Publications
        13.1  Additional Publications

    14  How to Learn More

1  Introduction

This guide provides additional information on the MetaCyc database (DB) beyond that found in other MetaCyc publications [1, 2, 3, 4, 5, 6, 7], to help users of the database understand its contents in more depth.

2  MetaCyc Overview

A unique property of MetaCyc is that it is curated[def] from the scientific experimental literature according to an extensive process  [6], such that:

• More than 2,216different organisms are represented

• The majority of pathways occur in microorganisms and plants

• More than 1,790metabolic pathways are stored, with more than 8,800enzymatic reactions and more than 33,541associated literature citations

• MetaCyc stores all enzyme-catalyzed reactions that have been assigned EC numbers by the Nomenclature Committee of the International Union of Biochemistry and Molecular Biology (NC-IUBMB)

• MetaCyc also stores thousands of additional enzyme-catalyzed reactions that have not yet been assigned an EC number

2.1  Motivations

Support computational metabolic network prediction

One of MetaCyc’s primary applications is to serve as a reference database for computationally predicting the metabolic network of an organism from its annotated genome, such as by the PathoLogic algorithm, part of Pathway Tools. [example]

Provide an encyclopedic reference on pathways and enzymes

MetaCyc is used as a readily accessible source of up-to-date, literature-curated information on metabolic pathways and enzymes by researchers for basic research and genome analysis, and by students and teachers for educational purposes. [example]

Support metabolic engineering

Metabolic engineers use MetaCyc as an encyclopedia of metabolic pathways and enzymes that may be genetically engineered into an organism to alter its metabolism. [example]

2.2  Database Contents

• Primary metabolism [def]

• Secondary metabolism [def]

MetaCyc also stores compounds, proteins, protein complexes and genes associated with these pathways.

MetaCyc is extensively linked to other biological databases [8] containing protein and nucleic-acid sequence data, bibliographic data and protein structures.

Unlike EcoCyc, MetaCyc provides little genomic data. MetaCyc does contain objects for the genes that encode most of the enzymes within the DB, but MetaCyc contains no sequence data. It does contain links to external sequence databases.

2.3  Query and Visualization

• Text-based searching, when trying to find information without knowing exactly how an object is named [example]

• Browsing using ontologies, when one wants to search by proceeding from general categories to specific instance [example]

• Direct queries, when an identifier is known [example]

Comparison features combine MetaCyc with other BioCyc databases to provide additional ways for viewing data. Examples for Cross-Species comparisons include:

• Comparing specific pathways between two or more organisms [example]

• Comparing the genomic maps of two or more organisms [example]

Additionally, a desktop version of the software provides substantially more powerful capabilities. When installed locally with multiple organism-specific databases, the desktop version enables several powerful capabilities, such as:

• Comparing the overall metabolic networks of different organisms [example]

The desktop version can be downloaded here.

2.4  The MetaCyc Data Universe

Figure 1:  Click here for examples of enzymes, pathways, compounds, reactions, and genes.

2.5  Linking to MetaCyc

Users are encouraged to link their Web site or application to MetaCyc as described here.

2.6  Development

MetaCyc is a collaborative project between SRI International, the Boyce Thomson Institute for Plant Research, and the Carnegie Institution of Washington. Since its beginning in 1998, MetaCyc’s data have been gathered from a variety of literature and on-line sources. A staff of several full-time curators update MetaCyc on an ongoing basis using a literature-based strategy.[def] [11]

2.7  Underlying Software

MetaCyc is based on the same retrieval and visualization software used by EcoCyc and other BioCyc databases - the Pathway Tools platform – which can be obtained here.

3  Position of MetaCyc Within the BioCyc Collection

MetaCyc is a member of the BioCyc collection of Pathway/Genome Databases. In contrast to all other members of that collection, which are organism-specific DBs, MetaCyc is a multiorganism DB. One goal of the MetaCyc project is for MetaCyc to contain a representative example of every experimentally determined metabolic pathway. All other BioCyc databases describe the metabolic network and genome of a single organism, and mix experimentally determined pathways with computationally predicted pathways.

MetaCyc does not seek to model the complete metabolism of any particular organism, which is the role of individual BioCyc DBs. Instead, MetaCyc serves as a high-quality reference DB for predicting metabolic pathways in other organisms. Scientists typically use MetaCyc to answer metabolic questions that span multiple domains of life, such as “what are all the pathways for arginine degradation in microbes,” or “what cofactor biosynthesis pathways are known in bacteria?” For questions that require information about the complete genome, proteome, or metabolic network of an organism, instead consult the organism-specific PGDB. For example, MetaCyc contains 14 pathways that have been experimentally studied in Staphylococcus aureus, and 36 enzymes that participate in these pathways. In contrast, the BioCyc Staphylococcus aureus RF122 PGDB contains 189 pathways (most of which are computationally predicted), plus the entire genome and proteome of that strain.

4  MetaCyc Availability

MetaCyc is available in several different forms to facilitate different uses of the data:

• The MetaCyc data are available through the MetaCyc Web site for interactive querying and visualization.

• The MetaCyc data can be downloaded as a set of data files. These files can be parsed and queried using languages like Perl, or they can be loaded into other database systems. Click here for more information about the flat files, or you can download them from here.

• A downloadable program that combines the Pathway Tools software with MetaCyc and the other BioCyc PGDBs can be installed on computers at your site, with the following advantages:

  • It provides some functionality that is not provided by the MetaCyc Web site, such as comparative analysis of entire metabolic pathways

  • It usually runs more quickly than the Web site

  • It supports programmatic querying of MetaCyc using APIs in the Java, Perl, and Lisp languages

  • It supports running an equivalent of the BioCyc Web site on your intranet

5  Release Frequency and History

New versions of MetaCyc are released four times per year.

• Two releases are “minor” releases, that is, data releases are made available on the MetaCyc.org Web site and in downloadable data files.

• Two releases are “major” releases, which include the updates available in minor releases, plus new versions of the downloadable Pathway Tools software that includes MetaCyc.

A detailed history of the enhancements to MetaCyc in each MetaCyc release is available here. This page also contains statistics on the size of MetaCyc over time.

6  MetaCyc Curation

The curation procedures that the MetaCyc curators follow are described in the Curator’s Guide to Pathway/Genome Databases.

MetaCyc data are derived from primary literature, from reviews, and from external databases.

For certain organisms, some of the data within MetaCyc have been directly imported from other databases which we consider to be the authoritative sources of data on those organisms:

• Arabidopsis thaliana: AraCyc

• Escherichia coli K-12: EcoCyc

• Saccharomyces cerevisiae S288C: Yeast Biochemical Pathways

• Streptomyces coelicolor A3(2): ScoCyc

6.1  Information Types Captured During the MetaCyc Curation Process

6.1.1  Pathways

A summary that includes:

• What the pathway does

• Its start point

• Its end product

• Relationship with other pathways

• Significance of the pathway

• Organism within which the pathway exists

• Experimental evidence for the pathway

• Contradictory evidence

• Citations

Other data:

        

• Synonyms

• Taxonomic range

• Key reactions

6.1.2  Reactions

• EC number of enzyme activities, if applicable

• Free energy of activation (Δ G)

• Comments, such as:

  • Whether this is a novel reaction

  • Whether this is a hypothetical reaction

  • Whether the reaction is spontaneous, in vitro or in vivo

  • Whether the reaction can be balanced

6.1.3  Enzymes and Enzyme Complexes

A summary that includes:

• Experimental evidence

• Isoforms

• Substrate specificity of each isoform

• Tissue type

• Subcellular localization

• Developmental stage

• Citations

Other data:

• Common name of the enzyme and synonym(s)

• Subcellular location

• Native molecular weight (KDa)

• Name of the enzymatic activity (for each reaction associated with the enzyme)

• Name(s) of cofactor(s), activator(s) and inhibitor(s)

• K_m

• pI

• Optimum pH

• Optimum temperature

6.1.4  Genes

• Common name of the gene and synonym(s)

• Citations

• A link to an external database that contains sequence information, such as Entrez Nucleotide or Gene.

6.1.5  Compounds

• Synonym(s) of the compound name

• Compound structure

• In some case, a summary describing the compound and its importance in Biology

7  Taxonomic Designations for Pathways

MetaCyc contains experimentally elucidated metabolic pathways. Every pathway in MetaCyc is labeled with the name of one or more taxonomic groups in which wet-lab experiments have indicated that the pathway is present. These taxonomic designations include species names, species and strain names, and names of higher taxa such as genus names, e.g., Pseudomonas. When a high-level taxon, such as a genus, is present as a pathway label, the interpretation is that experimental evidence suggests that the pathway is present in all members of that taxon.

The “number of organisms” row in the MetaCyc statistics indicates the total number of different organisms that are listed in the taxonomic designations of all MetaCyc pathways. There is wide variation in how many pathways a given taxon contributes to MetaCyc, with some taxa contributing only a single pathway, and other taxa contributing more than 100 pathways. The taxonomic distribution of MetaCyc pathways is summarized here: [Pathway Taxonomic Distribution] .

To query MetaCyc pathways by species:

• Web version: Select MetaCyc, then Search Menu → Pathways then expand Search/Filter by organism

• Desktop version: Select MetaCyc, then Pathway → Search by Organism

8  Database Links

MetaCyc contains links to many other bioinformatics DBs. Some MetaCyc links are “unification links”, meaning that they are links from an object in MetaCyc to an object in another DB that represents the same biological object. Other links are “relationship links”, meaning that they are links from an object in MetaCyc to an object in another DB that represents a related object, such as a link from a MetaCyc reaction to a PIR protein that catalyzes that reaction. The following types of MetaCyc objects contain links to the following databases.

• Pathways link to EcoCyc, the University of Minnesota Biocatalysis/Biodegradation Database, the KEGG Ligand database, and the Soybase database

• Proteins link to the UniProt/Swiss-Prot database

• Reactions link to the ENZYME database

• Chemical compounds link to the NCI Open Database, to PubChem, to ChEBI, to the Chemical Abstracts database and to Wikipedia.

• Genes link to NCBI Entrez nucleotide and gene databases, to TAIR (The Arabidopsis Information Resource) and to the Coli Genetic Stock Center

• All types of objects may contain literature citations, which link to PubMed when available

9  Data Sources

MetaCyc incorporates information that was obtained from the following sources:

The primary literature

Most of the data in MetaCyc is derived from primary literature. Every pathway and every enzyme are based on articles published in peer-reviewed magazines. Many literature citations are obtained via PubMed.

The EC list

The reactions in MetaCyc that have EC numbers were originally defined by the Nomenclature Committee of the International Union of Biochemistry and Molecular Biology (IUBMB), as seen in the ExplorEnz database. Most such “EC reactions” were imported into MetaCyc via the ENZYME database, an enzyme nomenclature database based on the recommendations of the IUBMB, with the kind permission of the Swiss Institute of Bioinformatics.

Subsequent to their import into MetaCyc, we have modified many of the EC reactions from the original IUBMB format. One main reason for the modifications is the fact that in MetaCyc the compounds that participate in the reactions are actually database objects, rather than strings of text. Although in the IUBMB and the ENZYME DB the same compound may be referred to by different names in different reactions, in MetaCyc reactions the compound will always be represented by a reference to the same underlying database entry for the compound, and thus will be referred to in MetaCyc reactions by the same common name. A second reason for modification is our attempt to provide a consistent format for the representation of reactions, in the form of “reactants ⇋ products”, which format is not always used by the IUBMB. For example, reaction EC 3.4.24.86, ADAM 17 endopeptidase, is defined by the IUBMB by the free text: “Narrow endopeptidase specificity. Cleaves Pro-Leu-Ala-Gln-Ala-|-Val-Arg-Ser-Ser-Ser in the membrane-bound, 26-kDa form of tumor necrosis factor alpha (TNF-alpha). Similarly cleaves other membrane-anchored, cell-surface proteins to ’shed’ the extracellular domains”. In MetaCyc the reaction is presented simply as “TNF-α ⇋ cleaved TNF-α”, and the rest of the information is provided within the reaction comment. An additional difference results from the fact that all MetaCyc compounds are protonated to a consistent pH (the cytosolic pH of 7.3), and all reactions are mass balanced for hydrogen by the addition of protons where applicable.

UniProt protein database

Most of the enzymes in MetaCyc are linked to UniProt. UniProt data is often used as the source for the enzyme’s molecular weight (calculated from sequence), for links to DNA sequence databases, and for synonyms of the enzyme and its gene. It is also used to help determine the taxonomic distribution of enzymes.

NCBI Taxonomy, Nucleotide and Gene databases

The NCBI taxonomy database is integrated into MetaCyc, and all internal references to organisms that are included in that taxonomy are based on the NCBI taxonomy IDs. MetaCyc gene entries are most commonly linked to the NCBI Nucleotide and Gene databases.

ChEBI, KEGG Ligand and PubChem chemical structure databases

While most of the chemical structures in MetaCyc were obtained from the original literature, some were obtained from other databases. MetaCyc entries contain DB links to many other compound databases, including ChEBI, KEGG and PubChem.

The BRENDA enzyme database

When predicting the taxonomic range of pathways, MetaCyc curators often use data from BRENDA to estimate the taxonomical range of individual enzymes.

10  Comparison of MetaCyc to other Pathway Databases

10.1  KEGG

KEGG is based on a set of “reference pathway maps.” A KEGG reference pathway map is typically compiled from multiple literature sources, and integrates reactions and pathways found in multiple species. The KEGG web site can display KEGG reference pathways with reactions colored to indicate which enzymes are predicted to be present from a given organism within a reference pathway. We call these diagrams “species views of reference pathways.”

The collection of pathways in MetaCyc is analogous to the KEGG reference pathway set, and the organism-specific PGDBs within BioCyc correspond to KEGG species views of reference pathways.

MetaCyc Compared to KEGG

MetaCyc version 13.5 (2009) contains 1,399 pathways, compared to the 155 pathways in KEGG version 50 (2009). Furthermore MetaCyc assigns more than twice as many of its reactions (4,950 in version 13.5) to pathways as does KEGG (2,463 in version 50).

We argue that MetaCyc pathways are closer to true biological pathways than are KEGG pathways. KEGG reference pathways are typically mosaics of related pathways from several different species. KEGG pathways are typically 3-4 times larger than are MetaCyc pathways because MetaCyc pathways attempt to model individual biological pathways from individual organisms. For example, the KEGG pathway called “methionine metabolism” combines pathways for the biosynthesis of methionine, charging of methionyl-tRNA, and conversion of methionine to other compounds such as N-formyl-methionine. The smaller pathways in MetaCyc are advantageous for several reasons. First, these smaller pathways correspond more closely to biologically meaningful units – meaningful in the sense that they correspond to a single biological function, they are regulated as a unit, and they tend to be conserved through evolution. These issues are discussed in more detail in [8], which discusses how these different pathway ontologies can affect computational analyses of pathway data.

By defining connected clusters of individual pathways, called superpathways (see the MetaCyc Pathway Ontology)”, MetaCyc does allow the user to view interconnections among several pathways, and to see the larger biochemical context in which a pathway operates. MetaCyc records separately the different pathway variants that have been observed in different organisms; KEGG does not explicitly record pathway variants. Within the large pathways defined by KEGG, it is impossible for the user to tell which subnetworks correspond to distinct biological units, nor in which species these units have been elucidated experimentally.

MetaCyc curators author extensive minireview summaries that describe individual pathways and enzymes. KEGG contains no such summaries.

MetaCyc cites the primary literature sources from which pathway and enzyme data were obtained. KEGG contains no literature citations, making the sources of KEGG data difficult to ascertain.

MetaCyc pathways are labeled with the name(s) of the species in which the presence of those pathways has been experimentally determined, whereas KEGG reference pathways do not state the species in which they were experimentally observed. Pathways in MetaCyc and in other BioCyc PGDBs contain evidence codes that indicate whether experimental or computational evidence supports the presence of the pathway in that organism; KEGG does not use evidence codes.

MetaCyc contains data on enzyme properties for specific enzymes from specific species, such as subunit composition, substrate specificity, cofactor requirements, activators, and inhibitors. KEGG has only cofactor data. However, because those data are associated with KEGG reactions rather than with KEGG enzymes, it is difficult to be sure for which proteins from which species the cofactor requirement was experimentally elucidated.

BioCyc Organism-Specific PGDBs Compared to KEGG Species Views of Reference Pathways

Data that are manually curated from the biological literature by biologist experts are generally preferable to computationally predicted data. Therefore, the curated organism-specific PGDBs in BioCyc, and those created by groups outside SRI for important organisms from Yeast to Arabidopsis, are preferable to KEGG pathway maps that are not curated on an organism-specific basis. PGDBs pathways are edited and customized to reflect species-specific variation of pathways (such as addition or deletion of reactions), whereas KEGG species views of reference pathways do not alter the reference pathways. This approach limits the accuracy of the KEGG species views since all reactions from the reference pathway are always visible, even when known not to occur in a given organism.

As of 2006, KEGG contained a large and systematic set of errors in the assignment of enzymes to reactions in its species views of reference pathways. These errors were caused by the improper use of partial EC numbers [[9].

BioCyc contains more than 600 organism-specific PGDBs. Some, such as the EcoCyc DB, have undergone extensive curation. The EcoCyc DB has undergone several person-decades worth of curation, for example. In contrast, it is not at all clear how much curation KEGG organism-specific DBs have undergone. The BioCyc Tier 3 PGDBs are regenerated on an ongoing basis.

All BioCyc PGDBs are completely free and open to all users, whereas the KEGG data are not.

BioCyc PGDBs are available in easily parsable, regular formats, that are accessible through many different data access mechanisms [3].

Pathway Tools Software Compared to KEGG Software

The Pathway Tools software that underlies MetaCyc and BioCyc is much more advanced than the KEGG software in many respects. Pathway Tools can be installed locally at your site, and you can use it to generate pathway predictions at your site. It has a number of other inference tools in addition to its pathway predictor, including a predictor of pathway hole fillers and an operon predictor. It supports painting of omics datasets onto pathway maps.

10.2  UM-BBD

The University of Minnesota Biocatalysis/Biodegradation Database contains (as of March 2008) 197pathways and 870enzymes from 510microorganisms. Pathways are curated from the biomedical literature, and do contain significant comments and literature citations. This database contains information on microbial biocatalytic reactions and biodegradation pathways for primarily xenobiotic, chemical compounds. The goal of the UM-BBD is to provide information on microbial enzyme-catalyzed reactions that are important for biotechnology.

10.3  Reactome

Reactome is a curated database of biological processes in humans. It covers biological pathways ranging from the basic processes of metabolism to high-level processes such as hormonal signaling. Reactome information is curated form the literature, and includes significant comments and literature citations. Reactome contains far fewer metabolic pathways than does MetaCyc, and because most Reactome pathways are curated based on human biology, Reactome does not have the taxonomic breadth of MetaCyc, although Reactome pathways have been computationally projected to a number of model organisms.

11  The MetaCyc Team

This section summarizes the many past and present contributors to the MetaCyc project.

11.1  Current Contributors

SRI International

Roles: Curation of non plant-related pathways, software development, Web site operations

• Peter D. Karp, Ph.D. - Bioinformatics Director

• Ron Caspi, Ph.D. - Curator

• Carol Fulcher, Ph.D. - Curator

• Anamika Kothari - Curator

• Tomer Altman - Scientific Programmer

• Markus Krummenacker - Bioinformatics Scientist

• Mario Latendresse, Ph.D. - Computer Scientist

• Quang Ong - Scientific Programmer

• Suzanne Paley - Computer Scientist

• Pallavi Subhraveti - Scientific Programmer

The Carnegie Institution of Washington

Role: Curation of plant-related pathways

• Kate Dreher, Ph.D. - Curator

• Peifen Zhang, Ph.D. - Curator

• Seung Yon (Sue) Rhee, Ph.D. - Director, TAIR

Boyce Thomson Institute for Plant Research

Role: Curation of plant-related pathways

• Lukas Mueller, Ph.D. - Director, SOL Genomics Network

11.2  MetaCyc Advisory Board

The MetaCyc Advisory Board advises the project on a variety of matters including task prioritization, database content, user interface issues, and community outreach. The advisors meet once per year. The current board members are listed here.

11.3  Past Contributors

• Martha Arnaud, Ph.D., Candida Genome Database, Stanford University

• Joseph M. Dale, formerly at SRI

• Hartmut Foerster, Ph.D., formerly at the Carnegie Institute of Washington, Plant Department

• John Ingraham, Ph.D., UC Davis

• Cindy Krieger, Ph.D., Saccharomyces Genome Database, Stanford University

• A. Karthikeyan, Ph.D, formerly at the Carnegie Institute of Washington, Plant Department

• Anuradha Pujar, Ph.D, Boyce Thomson Institute for Plant Research

• John Pick, formerly at SRI

• Liviu Popescu, formerly at SRI

• Sunita Reddy, formerly at SRI

• Fred Gilham, formerly at SRI

• Monica Riley, Ph.D., Marine Biological Laboratory

• Alfred Spormann, Ph.D., Stanford University

• Christophe Tissier, Ph.D., formerly at the Carnegie Institute of Washington, Plant Department

• Alfred Wang, formerly at Stanford University

12  Submitting Pathways for Incorporation into MetaCyc

We at MetaCyc would like to incorporate pathways created by other scientists into the database.

If you are a Pathway Tools user and have created a pathway that fits our criteria, why not send it to us? If we end up including it in MetaCyc, we will credit your contribution in the MetaCyc release notes, and if you wish, your name and your institution will appear on the pathway page.

In addition, by submitting pathways to MetaCyc you increase the power of the PathoLogic metabolic-pathway prediction software. PathoLogic recognizes MetaCyc pathways in genome sequence data, and is now in use by more than 100 groups worldwide.

If you would like to submit a pathway for inclusion in a future release of MetaCyc, please make sure that you curate the pathway following these guidelines:

• The pathway must be experimentally proven, and must be described in a published journal article

• Each pathway and enzyme must have summaries and literature citations

• Each pathway gene should have a link to a sequence database (e.g. Entrez); and a citation, if available

• Enzymes should have as much information as possible, such as optimal pH and temperature, K_m values, inhibitor, activator and cofactor information, etc.

• Please include evidence codes for enzymes and pathways

• Please make sure to use the Author Crediting feature (found within the Pathway Info Editor) to add the names of the curators and their institution affiliations . This will insure that the appropriate credit for your pathway is published on the BioCyc web page.

For examples of pathways that have been curated based on these guidelines, please see:

• formaldehyde oxidation VI

• ammonia oxidation I

• D-camphor degradation

Further information can be found in the Curator’s Guide for Pathway/Genome Databases.

12.1  How to Ensure that You and Your Organization Receive the Appropriate Credit

Pathway Tools includes an author crediting system that can attach author and organization credentials to individual pathways. We recommend that prior to creating new objects in the PGDB you should create an Organization frame for your institute and an Author frame for yourself. This way, items that you create afterwards will be associated with these frames, providing you with the credit that you deserve. This credit information would be retained upon exporting the pathways and importing them into MetaCyc. It is also possible to add credit information to older pathways that were created prior to the creation of your author frame, through the Pathway Info Editor.

Detailed instructions on how to create organization and author frames are found in the user manual, in the section ’Creating author frames’.

12.2  How to Send Pathways to MetaCyc

Pathways should be exported into a text file, which can be emailed to us at: .

The procedure for exporting a pathways is:

• Display the pathway in Pathway Tools; right click on its name and choose: Edit → Add pathway to file export list

• Repeat until you have added all pathways to be submitted

• From the file menu, choose: Export → Selected pathways to file

• Email us the resulting text file

Please indicate if you would like your name and/or affiliation to appear on the pathway and enzyme pages.

13  MetaCyc Publications

If you use MetaCyc in your research, we ask that you cite the following publication:

[MetaCyc12] Caspi, R., Altman, T., Dreher, K., Fulcher, C.A., Keseler, I.M., Kothari, A., Krummenacker, M., Latendresse, M., Mueller, L.A., Ong, Q., Paley, S., Pujar, A., Shearer, A., Subhraveti, P., Travers, M., Weerasinghe, D., Zhang, P. and Karp, P.D. (2012)
The MetaCyc Database of metabolic pathways and enzymes and the BioCyc collection of Pathway/Genome Databases
Nucleic Acids Research 40(1):D742-D753.

13.1  Additional Publications

[MetaCyc11] Karp, PD, and Caspi, R., A survey of metabolic databases emphasizing the MetaCyc family
Archives of Toxicology 85:1015–33 2011.

label[MetaCyc10] [MetaCyc10] Caspi, R., Altman, T., Dale, J.M., Dreher, K., Fulcher, C.A., Gilham, F., Kaipa, P., Karthikeyan, A.S., Kothari, A., Krummenacker, M., Latendresse, M., Mueller, L.A., Paley, S., Popescu, L., Pujar, A., Shearer, A., Zhang, P. and Karp, P.D. (2010)
The MetaCyc Database of metabolic pathways and enzymes and the BioCyc collection of Pathway/Genome Databases
Nucleic Acids Research 38(1):D473-D479.

[MetaCyc08] Caspi, R., Foerster, H., Fulcher, C.A., Kaipa, P., Krummenacker, M., Latendresse, M., Paley, S., Rhee, S.Y., Shearer, A., Tissier, C., Walk, T.C., Zhang, P. and Karp, P.D. (2008)
The MetaCyc Database of metabolic pathways and enzymes and the BioCyc collection of Pathway/Genome Databases
Nucleic Acids Research 36(1):D623–D631.

[MetaCyc06] Caspi, R., Foerster, H., Fulcher, C.A., Hopkinson, R., Ingraham, J., Kaipa, P., Krummenacker, M., Paley, S., Pick, J., Rhee, S.Y., Tissier, C., Zhang, P. and Karp, P.D. (2006)
MetaCyc: A multiorganism database of metabolic pathways and enzymes
Nucleic Acids Research, 34:D511–D516.

[MetaCyc04] Krieger, C.J., Zhang, P., Mueller, L.A., Wang, A., Paley, S., Arnaud, M., Pick, J., Rhee, S.Y., and Karp, P.D. (2004)
MetaCyc: A Multiorganism Database of Metabolic Pathways and Enzymes,
Nucleic Acids Research 32(1):D438–42.

[MetaCyc03] Karp, P.D. (2003)
The MetaCyc Metabolic Pathway Database
In: Metabolic Engineering, B. Kholodenko and H. Westerhoff eds., Horizon Scientific Press.

[MetaCyc02] Karp, P.D., Riley, M., Paley, S. and Pellegrini-Toole, A. (2002)
The MetaCyc Database
Nucleic Acids Research, 30(1):59–61.

[MetaCyc00] Karp, P.D., Riley, M., Saier, M., Paulsen, I.T., Paley, S., and Pellegrini-Toole, A. (2000)
The EcoCyc and MetaCyc Databases
Nucleic Acids Research, 28(1):56–59.

See also the BioCyc Publications Page.

14  How to Learn More

• BioCyc User’s Guide

• Pathway/Genome Database Concepts Guide

• How to Use a Pathway Tools Website

• How to download Pathway Tools and organism flat-file databases

References