If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
Locations of Mapped Genes:
|Superclasses:||Biosynthesis → Amino Acids Biosynthesis → Proteinogenic Amino Acids Biosynthesis → L-cysteine Biosynthesis|
The pathway of cysteine biosynthesis is a two-step conversion starting from L-serine and yielding L-cysteine.
This pathway is regulated at the genetic level in its second step, wtih both cysteine synthase isozymes being under the positive control of the cysteine-responsive transcription factor CysB. It is also subject to very strong feedback inhibition of its first step by the final pathway product, cysteine.
Although two cysteine synthase isozymes exist, only cysteine synthase A (CysK) forms a complex with serine acetyltransferase. CysK is also the only one of the two cysteine synthases that is required for cell viability on cysteine-free medium.
Both steps in this pathway are reversible. Based on genetic and proteomic data, it appears that the cysteine synthases may actually act as a sulfur scavenging system during sulfur starvation, stripping sulfur off of L-cysteine, generating any number of variant amino acids in the process.
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Boronat84: Boronat A, Britton P, Jones-Mortimer MC, Kornberg HL, Lee LG, Murfitt D, Parra F (1984). "Location on the Escherichia coli genome of a gene specifying O-acetylserine (thiol)-lyase." J Gen Microbiol 130(3);673-85. PMID: 6374031
Byrne88: Byrne CR, Monroe RS, Ward KA, Kredich NM (1988). "DNA sequences of the cysK regions of Salmonella typhimurium and Escherichia coli and linkage of the cysK regions to ptsH." J Bacteriol 1988;170(7);3150-7. PMID: 3290198
Denk87: Denk D, Bock A (1987). "L-cysteine biosynthesis in Escherichia coli: nucleotide sequence and expression of the serine acetyltransferase (cysE) gene from the wild-type and a cysteine-excreting mutant." J Gen Microbiol 1987;133 ( Pt 3);515-25. PMID: 3309158
DiazMejia09: Diaz-Mejia JJ, Babu M, Emili A (2009). "Computational and experimental approaches to chart the Escherichia coli cell-envelope-associated proteome and interactome." FEMS Microbiol Rev 33(1);66-97. PMID: 19054114
Diner12: Diner EJ, Beck CM, Webb JS, Low DA, Hayes CS (2012). "Identification of a target cell permissive factor required for contact-dependent growth inhibition (CDI)." Genes Dev 26(5);515-25. PMID: 22333533
Flint96: Flint DH, Tuminello JF, Miller TJ (1996). "Studies on the synthesis of the Fe-S cluster of dihydroxy-acid dehydratase in escherichia coli crude extract. Isolation of O-acetylserine sulfhydrylases A and B and beta-cystathionase based on their ability to mobilize sulfur from cysteine and to participate in Fe-S cluster synthesis." J Biol Chem 271(27);16053-67. PMID: 8663055
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Gao13: Gao Y, Peng X, Zhang J, Zhao J, Li Y, Li B, Hu Y, Chai Z (2013). "Cellular response of E. coli upon Hg2+ exposure--a case study of advanced nuclear analytical approach to metalloproteomics." Metallomics 5(7);913-9. PMID: 23771180
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