This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
|Superclasses:||Degradation/Utilization/Assimilation → Inorganic Nutrients Metabolism → Sulfur Compounds Metabolism|
Some taxa known to possess this pathway include : Paracoccus pantotrophus NKNCYSA
Expected Taxonomic Range: Bacteria
L-cysteate is a natural product first found in wool, and is an intermediate in cysteine metabolism involved in, for example, the synthesis of taurine in mammals [Weinstein88]. The compound also serves as a precursor of the cytophagal sulfolipid capnine [White84] and is found extracellularly in spiders' webs [Vollrath90].
Cysteate can serve as a sole source of carbon and energy for the aerobic growth of some bacteria [Stapley70, Rein05], as an electron acceptor for several sulfate-reducing bacteria [Lie96, Lie99], as an electron donor for some nitrate-reducing bacteria [Denger97, Mikosch99], and as the substrate for a fermentation in a sulfate-reducing bacterium [Laue97].
The nitrogen-reducing bacterium Paracoccus pantotrophus NKNCYSA can utilize L-cysteate as a sole source of carbon and energy for growth, with either nitrate or molecular oxygen as terminal electron acceptor [Mikosch99].
An inducible protein was found in extracts of cysteate-grown cells. The protein was purified and found to be 3-sulfolactate sulfo-lyase (encoded by suyA and suyB), an enzyme that catalyzes the conversion of (2R)-3-sulfolactate to pyruvate and bisulfite [Rein05].
Unlike the inducible 3-sulfolactate sulfo-lyase, the other two enzymes in this pathway are constitutive. The first reaction is the constitutive transamination of L-cysteate to 3-sulfopyruvate. It is still unclear whether a unique cysteate:2-oxoglutarate aminotransferase is expressed, or whether the reaction is catalyzed by a protein with another function (e.g. aspartate transaminase, EC 188.8.131.52).
The second reaction is an NAD-dependent reduction of 3-sulfopyruvate to (2R)-3-sulfolactate. This enzyme is constitutive as well. At the time of publication, it was not known whether a unique 3-sulfolactate dehydrogenase exists, or a malate dehydrogenase is involved. However, since then a specific L-2-hydroxycarboxylate dehydrogenase (NAD+) / (2R)-3-sulfolactate dehydrogenase, involved in coenzyme M biosynthesis, has been characterized from the archaeon Methanocaldococcus jannaschii [Graham02], and an NADP+-specific enzyme has been described in Chromohalobacter salexigens DSM 3043 [Denger10]. Both enzymes were named ComC (for CoM biosynthesis).
Denger10: Denger K, Cook AM (2010). "Racemase activity effected by two dehydrogenases in sulfolactate degradation by Chromohalobacter salexigens: purification of (S)-sulfolactate dehydrogenase." Microbiology 156(Pt 3);967-74. PMID: 20007648
Graham02: Graham DE, Xu H, White RH (2002). "Identification of coenzyme M biosynthetic phosphosulfolactate synthase: a new family of sulfonate-biosynthesizing enzymes." J Biol Chem 2002;277(16);13421-9. PMID: 11830598
Lie99: Lie TJ, Godchaux W, Leadbetter ER (1999). "Sulfonates as terminal electron acceptors for growth of sulfite-reducing bacteria (Desulfitobacterium spp.) and sulfate-reducing bacteria: effects of inhibitors of sulfidogenesis." Appl Environ Microbiol 65(10);4611-7. PMID: 10508097
Mikosch99: Mikosch CA, Denger K, Schafer EM, Cook AM (1999). "Anaerobic oxidations of cysteate: degradation via L-cysteate:2-oxoglutarate aminotransferase in Paracoccus pantotrophus." Microbiology 145 ( Pt 5);1153-60. PMID: 10376831
Rein05: Rein U, Gueta R, Denger K, Ruff J, Hollemeyer K, Cook AM (2005). "Dissimilation of cysteate via 3-sulfolactate sulfo-lyase and a sulfate exporter in Paracoccus pantotrophus NKNCYSA." Microbiology 151(Pt 3);737-47. PMID: 15758220
Vollrath90: Vollrath, F., Fairbrother, W. J., Williams, R. J. P., Tillinghast, E. K., Bernstein, D. T., Gallagher, K. S., Townley, M. A. (1990). "Compounds in the droplets of the orb spider's viscid spiral." Nature 345: 526-528.
Weinstein88: Weinstein CL, Griffith OW (1988). "Cysteinesulfonate and beta-sulfopyruvate metabolism. Partitioning between decarboxylation, transamination, and reduction pathways." J Biol Chem 263(8);3735-43. PMID: 3346220
Denger09: Denger K, Mayer J, Buhmann M, Weinitschke S, Smits TH, Cook AM (2009). "Bifurcated degradative pathway of 3-sulfolactate in Roseovarius nubinhibens ISM via sulfoacetaldehyde acetyltransferase and (S)-cysteate sulfolyase." J Bacteriol 191(18);5648-56. PMID: 19581363
Graupner00a: Graupner M, Xu H, White RH (2000). "Identification of an archaeal 2-hydroxy acid dehydrogenase catalyzing reactions involved in coenzyme biosynthesis in methanoarchaea." J Bacteriol 2000;182(13);3688-92. PMID: 10850983
Graupner01: Graupner M, White RH (2001). "The first examples of (S)-2-hydroxyacid dehydrogenases catalyzing the transfer of the pro-4S hydrogen of NADH are found in the archaea." Biochim Biophys Acta 1548(1);169-73. PMID: 11451450
Guidetti07: Guidetti P, Amori L, Sapko MT, Okuno E, Schwarcz R (2007). "Mitochondrial aspartate aminotransferase: a third kynurenate-producing enzyme in the mammalian brain." J Neurochem 102(1);103-11. PMID: 17442055
©2014 SRI International, 333 Ravenswood Avenue, Menlo Park, CA 94025-3493