PathwayStep2604 PathwayStep2585 PathwayStep2584 PathwayStep2583 PathwayStep2582 PathwayStep2590 PathwayStep2588 PathwayStep2589 PathwayStep2535 Methionine salvage pathway Cysteine formation from homocysteine Sulfur amino acid metabolism Authored: Stephan, R, 2010-10-24 Edited: Jassal, B, 2011-09-29 GENE ONTOLOGYGO:0000096 Pubmed16702333 Reactome Database ID Release 431614635 Reactome, http://www.reactome.org ReactomeREACT_115639 Reviewed: D'Eustachio, P, 2011-10-13 The main sulfur amino acids are methionine, cysteine, homocysteine and taurine. Of these, the first two are proteinogenic.<br><br>This group of reactions contains all processes that 1) break down sulfur amino acids, 2) interconvert between them, and 3) synthesize them from solved sulfide which comes from sulfate assimilation and reduction. Only plants and microorganisms employ all processes. Humans cannot de novo synthesize any sulfur amino acid, nor convert cysteine to methionine (Brosnan & Brosnan, 2006). Degradation of cysteine and homocysteine Methionine is reformed SAM is sythesized from methionine's reaction with ATP Remethylation of homocysteine via betaine degradation S-adenoylhomocysteine is hydrolyzed A dipeptidase cleaves cysteinylglycine Glutamate and cysteine combine