PathwayStep2603 PathwayStep2597 PathwayStep2592 PathwayStep2591 PathwayStep2594 PathwayStep2593 PathwayStep2596 PathwayStep2595 Degradation of cysteine and homocysteine Authored: Stephan, R, 2010-10-24 Edited: Jassal, B, 2011-09-29 GENE ONTOLOGYGO:0000098 Pubmed20162368 Reactome Database ID Release 431614558 Reactome, http://www.reactome.org ReactomeREACT_115654 Reviewed: D'Eustachio, P, 2011-10-13 While in humans excess methionine is converted to homocysteine, homocysteine and its transsulfuration product cysteine can be degraded to several end products, two of which, taurine and hydrogen sulfide, have uses in other biological processes (Stipanuk & Ueki 2011). Sulfide oxidation to sulfate Homocysteine is degraded to oxobutanoate and H2S CSAD decarboxylates 3-sulfinoalanine to hypotaurine Cysteine is oxidized Cysteine is degraded to serine and H2S Excess homocysteine yields homolanthionine and H2S Oxidation of hypotaurine to taurine Excess cysteine yields lanthionine and H2S