HumanCyc: Encyclopedia of Human Genes and Metabolism

HumanCyc provides an encyclopedic reference on human metabolic pathways. It provides a zoomable human metabolic map diagram, and it has been used to generate a steady-state quantitative model of human metabolism.

HumanCyc is part of the larger BioCyc collection of thousands of Pathway/Genome Databases for sequenced genomes. Click "change organism database" in the upper right corner to explore the available databases.

Subscriptions are now required to access HumanCyc. For more information on obtaining a subscription, click here. Why the transition to subscriptions?

Getting Started

New to HumanCyc? Typical usage includes:

  • Search for a gene or pathway using the Quick Search box at the upper right, or use the Search menu
  • Analyze human metabolomics and gene-expression data

For more information on HumanCyc, see our article "Computational prediction of human metabolic pathways from the complete human genome" in Genome Biology.

User Guide >>
  • Blood Cells

    put in the public domain by NCI/Donald BlissBruce Wetzel and Harry Schaefer.

    Heme, Not Just the Red Pigment in Blood.

    Heme, an iron-containing porphyrin, functions as a prosthetic group in numerous proteins. These range from components of the electron transport chain to many enzymes. No wonder the biosynthesis of heme is highly conserved in evolution!

    Learn More
  • Cellular Overview

    Cellular overview image generated by Pathway Tools

    Navigate Metabolic Map for Pathways

    The Cellular Overview enables you to browse through a zoomable metabolic map diagram that displays pathways according to groups based on biological function, or classes of metabolites produced/consumed.

    Learn More
  • Mitochondria, mammalian lung - TEM

    colorized selection from Mitochondria, mammalian lung - TEMput in the Public Domain by author, Louisa Howard.

    Important Mammalian Pathways: The Urea Cycle

    The urea cycle is responsible for mediating excretion of nitrogenous waste. It was the first metabolic pathway to be discovered, five years before the discovery of the TCA cycle. The cycle occurs across both the cytosol and the mitchondrion.

    Learn More
  • Route Search Diagram


    RouteSearch: Search for Paths through the Metabolic Network

    Search for lowest-cost paths through the metabolic network of the selected organism. Or, design lowest-cost pathways to novel compounds by adding reactions from MetaCyc.

    Learn More
  • Brain MRI

    selection from Brain MRI Source: Dr. Leon Kaufman. UCSF.

    A Pathway Linked to Central Nervous System Disorders

    The GABA shunt forms a closed loop in the CNS for conserving the supply of the excitatory neurotransmitter GABA. One of the enzymes of this pathway, 4-aminobutyrate aminotransferase is a target for the anti-epileptic drug vigabatrin.

    Learn More
  • SmartTable display generated by Pathway Tools.

    Metabolomics Data Analysis

    Multiple tools are available in this website for metabolomics data analysis.

    Learn More
  • The Truth about the Thanksgiving Turkey...

    Of the 20 amino acids, at least 9 are essential. Essential L-tryptophan is required for serotonin, melatonin and niacin synthesis. Its requirement for NAD biosynthesis was discovered when humans stricken with pellagra recovered after the addition of tryptophan or niacin to their diets.

    Learn More
  • Cellular Overview Omics Viewer image generated by Pathway Tools.

    Gene Expression Data Analysis

    Multiple tools are available in this website for analysis of gene expression data.

    Learn More


HumanCyc provides tools for querying, visualizing, and analyzing the underlying database, and for analyzing omics data:

  • Multiple pathway-analysis methods are available for omics and multi-omics datasets including painting data onto pathway diagrams and the metabolic-map diagram
  • Store groups of genes and pathways in your account as SmartTables; share, analyze, transform those groups
  • Search for paths in the metabolic network using the Metabolism → Metabolic Route Search tool

HumanCyc Curation

Curation primarily affects information on pathways and corresponding enzyme pages. HumanCyc is a partially curated database and is a work in progress; it is incomplete in many respects, and may contain errors.

HumanCyc contains few signaling pathways. It is not yet compartmentalized nor tissue-specific.

For information regarding most recently curated pathways see the Release Notes.

Video Tutorials

HumanCyc is built on the same software platform as Biocyc: Pathway Tools. The BioCyc webinar series introduces users to the basic and advanced features of the Pathway Tools software in the context of BioCyc. A complete list of videos in additional download formats are available on the Video and Podcast page.

This video introduces the site and the BioCyc collection of hundreds of Pathway/Genome Databases and covers:

  • BioCyc site contents, including EcoCyc, MetaCyc, and our extensive database collection
  • How to search, browse, and find what you need in the BioCyc collection
  • How we represent metabolism, transcription, and all their parts