Updated Pathways

Release Notes for YeastCyc Version 19.1

Released on June 25, 2015

Two pathways have been revised during this release. Updated Pathways

Release Notes for YeastCyc Version 18.5

Released on Nov 7th, 2014

One new primary pathway has been added during this release. Only a truncated version of the γ-glutamyl cycle comprising the overall biosynthetic and degradation steps of glutathione operates in Saccharomyces cerevisiae. The new pathway, coined DUG (Defective in Utilization of Glutathione) pathway, describes the catalytic reactions involved in the degradation of glutathione. The cytosolic DUG pathway appears to be essential for the maintenance of glutathione homeostasis in the cell and rules out the involvement of the only other glutathione degrading enzyme in yeast, i.e. the vacuolar gamma-glutamyl transpeptidase encoded by ECM38 in this process. New Pathways

Release Notes for YeastCyc Version 18.0

Released on March 24, 2014

The new primary metabolic pathways added to YeastCyc include the biosynthesis of fatty acids, cofactors and vitamin B1 derivatives (thiamine triphosphate). Lipoate is an essential sulfur-containing cofactor that is responsible for the lipoylation of the E2 subunits of mitochondrial enzymes involved in mitochondrial maintenance and respiratory growth in yeast. The biosynthesis and incorporation of lipoate has been depicted for three mitochondrial enzymes, i.e. pyruvate dehydrogenase, α-ketoglutarate dehydrogenase and the glycine cleavage enzyme which catalyze the oxidative decarboxylation of glycolysis end products and TCA cycle intermediates, hence connecting cytosolic glycolysis with mitochondrial respiration. The pathway for the direct precursor of lipoate, i.e. octanoyl-[acp] has also been added to YeastCyc. This pathway takes place in the mitochondria and is catalyzed by individual type II fatty acid synthases.

Other yeast pathways describe the remodeling of phospholipids, e.g. phosphoethanolamine, phosphatidylcholine and phsophatidate involved in the homeostasis of cell membrane glycerophospholipids, as well as a pathway illustrating the metabolism of main precursor monoacylglycerols. Another pathway involved in the integrity and functioning of cell membranes, the sterol:steryl ester interconversion, has also been characterized. This pathway controls the amount of free sterols present in the cell which are available for incorporation into cell membranes. Thiamin (vitamin B1) and its phosphate derivative are involved in many aspects of cellular metabolism. The new pathway describes the synthesis of thiamin triphosphate which apparently does not act as a cofactor but may be involved in protein activation and mediator in signaling pathways. New Pathways

New Superpathways

Updated Pathways

Release Notes for YeastCyc Version 17.5

Released on Ocrober 11, 2013

Since the last release 14 new pathways have been added to YeastCyc. Furthermore, 4 existing pathways were extensively revised by adding new gene and enzyme information and updating the respective pathway commentary. The new primary metabolic pathways added to YeastCyc include the biosynthesis and degradation of fatty acids and vitamin B1 (thiamine).

Fatty acids fulfill many essential functions in plants, animals and fungi. They determine membrane composition, integrity, and function, are involved in signaling pathways, participate in post-translational protein modification and serve as energy substrates. Yeast can grow on fatty acids as sole carbon source. Saturated fatty acids are completely degraded in the yeast peroxisomal β-oxidation cycle but activated unsaturated fatty acids with cis-, and/or cis/trans-double bonds at odd-numbered positions entail the involvement of so-called auxiliary enzymes which are employed in various pathways to utilize oleoyl-CoA, 10-cis/trans-heptadecenoyl-CoA and 9-cis,11-trans-octadecenoyl-CoA. In addition, the pathway describing the unique regulation of phosphatidylglycerol, a biosynthetic intermediate of the major anionic mitochondrial phospholipid cardiolipin has been added. Another new pathway delineates a resynthesis pathway of phosphatidylcholine, an important eukaryotic membrane phospholipid, operating supplemental to the two known biosynthetic routes for phosphatidylcholine formation in yeast.

 Thiamine (vitamin B1) and its phosphate derivatives are involved in many aspects of cellular metabolism, e.g. as indispensable co-factor in carbohydrate and amino acid catabolism. The new pathways describe the synthesis of the pyrimidine moiety in yeast which differs from both animal and plant pathways, and additional salvage pathways of thiamine catalyzed by bifunctional (TMP diphosphorylase/hydroxyethylthiazole kinase – THI6) and trifunctional (HMP/HMP-P kinase/thiaminase II – THI20) enzymes. The latter has even the enzymatic scope to catalyze the hydrolytic cleavage of synthetic antagonists, i.e. pyrithiamine and oxythiamine for the formation of thiamine in yeast.

Updated Pathways

Release Notes for YeastCyc Version 17.1

Released on June 11, 2013

The pyridine nucleotides NADH and NADPH play pivotal roles in energy metabolism, electron transfer, and indispensable metabolic cycles of yeast as well as in the maintenance of the cellular redox status and participation in signaling pathways. In this release we added the pathways delineating the interconversion of the major oxidized and reduced forms NAD/NADH and NADP/NADPH in mitochondria and the cytosol, which are carried out by different sets of enzymes.

Another addition for this release was the yeast aerobic respiration pathway, which differs from the plant and animal version by the absence of complex I.

New Superpathways

Updated Pathways

Release Notes for YeastCyc Version 17.0

Released on March 28, 2013

Several major changes have happened in this release.

Since its creation in 2002 and until 2013 YeastCyc has been developed solely by SGD curators. During that period YeastCyc has diverged significantly from other BioCyc databases due to parallel creation of compounds, reactions and pathways. This has led to difficulties in comparing the metabolism of Saccharomyces cerevisiae with that of other organisms included in the BioCyc collection.

In early 2012 the database was moved to SRI International, where it will be curated by both SGD curators and SRI curators. Several projects accompanied the transition:

Genome Update: The Saccharomyces cerevisiae genome used for generating the original database was only partially annotated, leading to many missing genes. The genome annotation has now been updated, resulting in a dramatic increase in the number of polypeptides from 837 to 5876.

Database synchronization: A significant effort was spent synchronizing the compounds, reactions and pathways between YeastCyc and MetaCyc, resulting in full synchronization of compounds and reactions, and much increased synchronization of pathways.

Re-evaluation of Pathways: The pathway prediction algorithm of Pathway Tools was run again on YeastCyc, and the resulting recommendations were reviewed manually by SRI curators, resulting in replacement of many of the existing pathways with more current pathways from MetaCyc, as well as incorporation of many new pathways. Existing pathways that have been created especially for S. cerevisiae by SGD curators that were deemed more appropriate than the MetaCyc pathways were left in the database. The total number of pathways increased from 154 to 239.

Change of version numbers: From now on the version number of YeastCyc will be the same as the version numbers of all other BioCyc databases.