EC 2.3.1.30     
Accepted name: serine O-acetyltransferase
Reaction: acetyl-CoA + L-serine = CoA + O-acetyl-L-serine
Glossary: O-acetyl-L-serine = (2S)-3-acetyloxy-2-aminopropanoic acid
Other name(s): SATase; L-serine acetyltransferase; serine acetyltransferase; serine transacetylase
Systematic name: acetyl-CoA:L-serine O-acetyltransferase
References:
1.  Kredich, N.M. and Tomkins, G.M. The enzymic synthesis of L-cysteine in Escherichia coli and Salmonella typhimurium. J. Biol. Chem. 241 (1966) 4955–4965. [PMID: 5332668]
2.  Smith, I.K. and Thompson, J.F. Purification and characterization of L-serine transacetylase and O-acetyl-L-serine sulfhydrylase from kidney bean seedlings (Phaseolus vulgaris). Biochim. Biophys. Acta 227 (1971) 288–295. [PMID: 5550822]
[EC 2.3.1.30 created 1972]
 
 
EC 2.5.1.47     
Accepted name: cysteine synthase
Reaction: O-acetyl-L-serine + hydrogen sulfide = L-cysteine + acetate
Glossary: O-acetyl-L-serine = (2S)-3-acetyloxy-2-aminopropanoic acid
Other name(s): O-acetyl-L-serine sulfhydrylase; O-acetyl-L-serine sulfohydrolase; O-acetylserine (thiol)-lyase; O-acetylserine (thiol)-lyase A; O-acetylserine sulfhydrylase; O3-acetyl-L-serine acetate-lyase (adding hydrogen-sulfide); acetylserine sulfhydrylase; cysteine synthetase; S-sulfocysteine synthase; 3-O-acetyl-L-serine:hydrogen-sulfide 2-amino-2-carboxyethyltransferase; O3-acetyl-L-serine:hydrogen-sulfide 2-amino-2-carboxyethyltransferase
Systematic name: O-acetyl-L-serine:hydrogen-sulfide 2-amino-2-carboxyethyltransferase
Comments: A pyridoxal-phosphate protein. Some alkyl thiols, cyanide, pyrazole and some other heterocyclic compounds can act as acceptors. Not identical with EC 2.5.1.51 (β-pyrazolylalanine synthase), EC 2.5.1.52 (L-mimosine synthase) and EC 2.5.1.53 (uracilylalanine synthase).
References:
1.  Becker, M.A., Kredich, N.M. and Tomkins, G.M. The purification and characterization of O-acetylserine sulfhydrylase-A from Salmonella typhimurium. J. Biol. Chem. 244 (1969) 2418–2427. [PMID: 4891157]
2.  Hara, S., Payne, M.A., Schnackerz, K.D. and Cook, P.F. A rapid purification procedure and computer-assisted sulfide ion selective electrode assay for O-acetylserine sulfhydrylase from Salmonella typhimurium. Protein Expr. Purif. 1 (1990) 70–76. [PMID: 2152186]
3.  Ikegami, F., Kaneko, M., Lambein, F., Kuo, Y.-H. and Murakoshi, I. Difference between uracilylalanine synthases and cysteine synthases in Pisum sativum. Phytochemistry 26 (1987) 2699–2704.
4.  Murakoshi, I., Kaneko, M., Koide, C. and Ikegami, F. Enzymatic-synthesis of the neuroexcitatory amino-acid quisqualic by cysteine synthase. Phytochemistry 25 (1986) 2759–2763.
5.  Tai, C.H., Burkhard, P., Gani, D., Jenn, T., Johnson, C. and Cook, P.F. Characterization of the allosteric anion-binding site of O-acetylserine sulfhydrylase. Biochemistry 40 (2001) 7446–7452. [PMID: 11412097]
6.  Bettati, S., Benci, S., Campanini, B., Raboni, S., Chirico, G., Beretta, S., Schnackerz, K.D., Hazlett, T.L., Gratton, E. and Mozzarelli, A. Role of pyridoxal 5′-phosphate in the structural stabilization of O-acetylserine sulfhydrylase. J. Biol. Chem. 275 (2000) 40244–40251. [PMID: 10995767]
[EC 2.5.1.47 created 1972 as EC 4.2.99.8, modified 1976, modified 1990, transferred 2002 to EC 2.5.1.47]
 
 
EC 2.5.1.50     
Accepted name: zeatin 9-aminocarboxyethyltransferase
Reaction: O-acetyl-L-serine + zeatin = lupinate + acetate
Glossary: lupinate = (S)-2-amino-3-{[(E)-4-hydroxy-3-methylbut-2-enylamino]purin-9-yl}propanoate
zeatin = (E)-2-methyl-4-(9H-purin-6-ylamino)but-2-en-1-ol = (E)-N6-(4-hydroxy-3-methylbut-2-enyl)adenine
O-acetyl-L-serine = O3-acetyl-L-serine = (2S)-3-acetyloxy-2-aminopropanoic acid
Other name(s): β-(9-cytokinin)-alanine synthase; β-(9-cytokinin)alanine synthase; O-acetyl-L-serine acetate-lyase (adding N6-substituted adenine); lupinate synthetase; lupinic acid synthase; lupinic acid synthetase; 3-O-acetyl-L-serine:zeatin 2-amino-2-carboxyethyltransferase
Systematic name: O-acetyl-L-serine:zeatin 2-amino-2-carboxyethyltransferase
Comments: The enzyme acts not only on zeatin but also on other N6-substituted adenines. The reaction destroys their cytokinin activity and forms the corresponding 3-(adenin-9-yl)-L-alanine.
References:
1.  Entsch, B., Parker, C.W. and Letham, D.S. An enzyme from lupin seeds forming alanine derivatives of cytokinins. Phytochemistry 22 (1983) 375–381.
2.  Mok, D.W.S. and Mok, M.C. Cytokinin metabolism and action. Ann. Rev. Plant Physiol. Plant Mol. Biol. 52 (2001) 89–118.
[EC 2.5.1.50 created 1984 as EC 4.2.99.13, transferred 2002 to EC 2.5.1.50]
 
 
EC 2.5.1.51     
Accepted name: β-pyrazolylalanine synthase
Reaction: O-acetyl-L-serine + pyrazole = 3-(pyrazol-1-yl)-L-alanine + acetate
Glossary: O-acetyl-L-serine = (2S)-3-acetyloxy-2-aminopropanoic acid
Other name(s): β-(1-pyrazolyl)alanine synthase; β-pyrazolealanine synthase; β-pyrazolylalanine synthase (acetylserine); O3-acetyl-L-serine acetate-lyase (adding pyrazole); BPA-synthase; pyrazolealanine synthase; pyrazolylalaninase; 3-O-acetyl-L-serine:pyrazole 1-(2-amino-2-carboxyethyl)transferase; O3-acetyl-L-serine:pyrazole 1-(2-amino-2-carboxyethyl)transferase
Systematic name: O-acetyl-L-serine:pyrazole 1-(2-amino-2-carboxyethyl)transferase
Comments: The enzyme is highly specific for acetylserine and pyrazole. Not identical with EC 2.5.1.52 L-mimosine synthase.
References:
1.  Murakoshi, I., Ikegami, F., Hinuma, Y. and Hanma, Y. Purification and characterization of β-(pyrazol-1-yl)-L-alanine synthase from Citrullus vulgaris. Phytochemistry 23 (1984) 973–977.
2.  Murakoshi, I., Ikegami, F., Hinuma, Y. and Hanma, Y. Purification and characterization of L-mimosine synthase from Leucaena leucocephala. Phytochemistry 23 (1984) 1905–1908.
3.  Murakoshi, I., Kuramoto, H. and Haginiwa, J. The enzymic synthesis of β-substituted alanines. Phytochemistry 11 (1972) 177–182.
4.  Noji, M., Murakoshi, I. and Saito, K. Evidence for identity of β-pyrazolealanine synthase with cysteine synthase in watermelon: formation of β-pyrazole-alanine by cloned cysteine synthase in vitro and in vivo. Biochem. Biophys. Res. Commun. 197 (1993) 1111–1117. [PMID: 8280125]
[EC 2.5.1.51 created 1989 as EC 4.2.99.14 (EC 4.2.99.17 incorporated 1992), transferred 2002 to EC 2.5.1.51]
 
 
EC 2.5.1.52     
Accepted name: L-mimosine synthase
Reaction: O-acetyl-L-serine + 3,4-dihydroxypyridine = 3-(3,4-dihydroxypyridin-1-yl)-L-alanine + acetate
Glossary: O-acetyl-L-serine = (2S)-3-acetyloxy-2-aminopropanoic acid
L-mimosine = (2S)-2-amino-3-(3-hydroxy-4-oxopyridin-1(4H)-yl)propanoic acid
Other name(s): O3-acetyl-L-serine acetate-lyase (adding 3,4-dihydroxypyridin-1-yl); 3-O-acetyl-L-serine:3,4-dihydroxypyridine 1-(2-amino-2-carboxyethyl)transferase; O3-acetyl-L-serine:3,4-dihydroxypyridine 1-(2-amino-2-carboxyethyl)transferase
Systematic name: O-acetyl-L-serine:3,4-dihydroxypyridine 1-(2-amino-2-carboxyethyl)transferase
Comments: Brings about the biosynthesis of L-mimosine in plants of the Mimosa and Leucaena genera. Not identical with EC 2.5.1.51, β-pyrazolylalanine synthase.
References:
1.  Murakoshi, I., Ikegami, F., Hinuma, Y. and Hanma, Y. Purification and characterization of β-(pyrazol-1-yl)-L-alanine synthase from Citrullus vulgaris. Phytochemistry 23 (1984) 973–977.
2.  Murakoshi, I., Ikegami, F., Hinuma, Y. and Hanma, Y. Purification and characterization of L-mimosine synthase from Leucaena leucocephala. Phytochemistry 23 (1984) 1905–1908.
3.  Murakoshi, I., Kuramoto, H. and Haginiwa, J. The enzymic synthesis of β-substituted alanines. Phytochemistry 11 (1972) 177–182.
4.  Noji, M., Murakoshi, I. and Saito, K. Evidence for identity of β-pyrazolealanine synthase with cysteine synthase in watermelon: formation of β-pyrazole-alanine by cloned cysteine synthase in vitro and in vivo. Biochem. Biophys. Res. Commun. 197 (1993) 1111–1117. [PMID: 8280125]
[EC 2.5.1.52 created 1989 as EC 4.2.99.15, transferred 2002 to EC 2.5.1.52]
 
 
EC 2.5.1.53     
Accepted name: uracilylalanine synthase
Reaction: O-acetyl-L-serine + uracil = 3-(uracil-1-yl)-L-alanine + acetate
Glossary: O-acetyl-L-serine = (2S)-3-acetyloxy-2-aminopropanoic acid
3-(uracil-1-yl)-L-alanine = L-willardiine
3-(uracil-3-yl)-L-alanine = L-isowillardiine
Other name(s): O3-acetyl-L-serine acetate-lyase (adding uracil); isowillardiine synthase; willardiine synthase; 3-O-acetyl-L-serine:uracil 1-(2-amino-2-carboxyethyl)transferase; O3-acetyl-L-serine:uracil 1-(2-amino-2-carboxyethyl)transferase
Systematic name: O-acetyl-L-serine:uracil 1-(2-amino-2-carboxyethyl)transferase
Comments: The enzyme produces the non-proteinogenic amino acid L-willardiine, which is naturally found in the plants Acacia willardiana, Mimosa pigra, and Pisum sativum (pea). The enzyme from Pisum species also produces L-isowillardiine. Not identical with EC 2.5.1.47 cysteine synthase.
References:
1.  Ahmmad, M.A.S., Maskall, C.S. and Brown, E.G. Partial-purification and properties of willardiine and synthase activity from Pisum sativum. Phytochemistry 23 (1984) 265–270.
2.  Ikegami, F., Kaneko, M., Lambein, F., Kuo, Y.-H. and Murakoshi, I. Difference between uracilylalanine synthases and cysteine synthases in Pisum sativum. Phytochemistry 26 (1987) 2699–2704.
3.  Murakoshi, I., Ikegami, F., Ookawa, N., Ariki, T., Haginiwa, J., Kuo, Y.-H. and Lambein, F. Biosynthesis of the uracilylalanines willardiine and isowillardiine in higher plants. Phytochemistry 17 (1978) 1571–1576.
[EC 2.5.1.53 created 1990 as EC 4.2.99.16, transferred 2002 to EC 2.5.1.53]
 
 
EC 2.5.1.118     
Accepted name: β-(isoxazolin-5-on-2-yl)-L-alanine synthase
Reaction: O-acetyl-L-serine + isoxazolin-5-one = 3-(5-oxoisoxazolin-2-yl)-L-alanine + acetate
Systematic name: O-acetyl-L-serine:isoxazolin-5-one 2-(2-amino-2-carboxyethyl)transferase
Comments: The enzyme from the plants Lathyrus odoratus (sweet pea) and L. sativus (grass pea) also forms 3-(5-oxoisoxazolin-4-yl)-L-alanine in vitro (cf. EC 2.5.1.119). However, only 3-(5-oxoisoxazolin-2-yl)-L-alanine is formed in vivo. 3-(5-oxoisoxazolin-2-yl)-L-alanine is the biosynthetic precursor of the neurotoxin N3-oxalyl-L-2,3-diaminopropanoic acid, the cause of lathyrism. Closely related and possibly identical to EC 2.5.1.47, cysteine synthase, and EC 2.5.1.51, β-pyrazolylalanine synthase.
References:
1.  Ikegami, F., Kamiya, M., Kuo, Y.H., Lambein, F. and Murakoshi, I. Enzymatic synthesis of two isoxazolylalanine isomers by cysteine synthases in Lathyrus species. Biol. Pharm. Bull. 19 (1996) 1214–1215. [PMID: 8889043]
[EC 2.5.1.118 created 2014]
 
 
EC 2.5.1.119     
Accepted name: β-(isoxazolin-5-on-4-yl)-L-alanine synthase
Reaction: O-acetyl-L-serine + isoxazolin-5-one = 3-(5-oxoisoxazolin-4-yl)-L-alanine + acetate
Systematic name: O-acetyl-L-serine:isoxazolin-5-one 4-(2-amino-2-carboxyethyl)transferase
Comments: 3-(5-Oxoisoxazolin-4-yl)-L-alanine is an antifungal antibiotic produced by the bacterium Streptomyces platensis. The enzymes from the plants Lathyrus odoratus (sweet pea), L. sativus (grass pea) and Citrullus vulgaris (watermelon) that catalyse EC 2.5.1.118 (β-(isoxazolin-5-on-2-yl)-L-alanine synthase) also catalyse this reaction in vitro, but not in vivo. Closely related and possibly identical to EC 2.5.1.47, cysteine synthase, and EC 2.5.1.51, β-pyrazolylalanine synthase.
References:
1.  Ikegami, F., Kamiya, M., Kuo, Y.H., Lambein, F. and Murakoshi, I. Enzymatic synthesis of two isoxazolylalanine isomers by cysteine synthases in Lathyrus species. Biol. Pharm. Bull. 19 (1996) 1214–1215. [PMID: 8889043]
[EC 2.5.1.119 created 2014]
 
 
EC 2.5.1.134     
Accepted name: cystathionine β-synthase (O-acetyl-L-serine)
Reaction: O-acetyl-L-serine + L-homocysteine = L-cystathionine + acetate
Other name(s): MccB; O-acetylserine dependent cystathionine β-synthase
Systematic name: O-acetyl-L-serine:L-homocysteine 2-amino-2-carboxyethyltransferase
Comments: A pyridoxal 5′-phosphate protein. The enzyme, purified from the bacterium Bacillus subtilis, also has a low activity with L-serine (cf. EC 4.2.1.22, cystathionine β-synthase).
References:
1.  Hullo, M.F., Auger, S., Soutourina, O., Barzu, O., Yvon, M., Danchin, A. and Martin-Verstraete, I. Conversion of methionine to cysteine in Bacillus subtilis and its regulation. J. Bacteriol. 189 (2007) 187–197. [PMID: 17056751]
[EC 2.5.1.134 created 2016]
 
 
EC 2.5.1.144     
Accepted name: S-sulfo-L-cysteine synthase (O-acetyl-L-serine-dependent)
Reaction: O-acetyl-L-serine + thiosulfate = S-sulfo-L-cysteine + acetate
Glossary: O-acetyl-L-serine = (2S)-3-acetyloxy-2-aminopropanoic acid
Other name(s): cysteine synthase B; cysM (gene name); CS26 (gene name)
Systematic name: O-acetyl-L-serine:thiosulfate 2-amino-2-carboxyethyltransferase
Comments: In plants, the activity is catalysed by a chloroplastic enzyme that plays an important role in chloroplast function and is essential for light-dependent redox regulation within the chloroplast. The bacterial enzyme also catalyses the activity of EC 2.5.1.47, cysteine synthase. cf. EC 2.8.5.1, S-sulfo-L-cysteine synthase (3-phospho-L-serine-dependent).
References:
1.  Hensel, G. and Truper, H.G. O-Acetylserine sulfhydrylase and S-sulfocysteine synthase activities of Rhodospirillum tenue. Arch. Microbiol. 134 (1983) 227–232. [PMID: 6615127]
2.  Nakamura, T., Iwahashi, H. and Eguchi, Y. Enzymatic proof for the identity of the S-sulfocysteine synthase and cysteine synthase B of Salmonella typhimurium. J. Bacteriol. 158 (1984) 1122–1127. [PMID: 6373737]
3.  Bermudez, M.A., Paez-Ochoa, M.A., Gotor, C. and Romero, L.C. Arabidopsis S-sulfocysteine synthase activity is essential for chloroplast function and long-day light-dependent redox control. Plant Cell 22 (2010) 403–416. [PMID: 20179139]
4.  Bermudez, M.A., Galmes, J., Moreno, I., Mullineaux, P.M., Gotor, C. and Romero, L.C. Photosynthetic adaptation to length of day is dependent on S-sulfocysteine synthase activity in the thylakoid lumen. Plant Physiol. 160 (2012) 274–288. [PMID: 22829322]
5.  Gotor, C. and Romero, L.C. S-sulfocysteine synthase function in sensing chloroplast redox status. Plant Signal Behav 8:e23313 (2013). [PMID: 23333972]
[EC 2.5.1.144 created 2018]
 
 
EC 2.6.99.3     
Accepted name: O-ureido-L-serine synthase
Reaction: O-acetyl-L-serine + hydroxyurea = O-ureido-L-serine + acetate
Glossary: O-ureido-L-serine = (2S)-2-amino-3-[(carbamoylamino)oxy]propanoate
O-acetyl-L-serine = O3-acetyl-L-serine = (2S)-3-acetyloxy-2-aminopropanoic acid
Other name(s): dcsD (gene name)
Systematic name: O-acetyl-L-serine:hydroxyurea 2-amino-2-carboxyethyltransferase
Comments: The enzyme participates in the biosynthetic pathway of D-cycloserine, an antibiotic substance produced by several Streptomyces species. Also catalyses EC 2.5.1.47, cysteine synthase.
References:
1.  Kumagai, T., Koyama, Y., Oda, K., Noda, M., Matoba, Y. and Sugiyama, M. Molecular cloning and heterologous expression of a biosynthetic gene cluster for the antitubercular agent D-cycloserine produced by Streptomyces lavendulae. Antimicrob. Agents Chemother. 54 (2010) 1132–1139. [PMID: 20086163]
2.  Uda, N., Matoba, Y., Kumagai, T., Oda, K., Noda, M. and Sugiyama, M. Establishment of an in vitro D-cycloserine-synthesizing system by using O-ureido-L-serine synthase and D-cycloserine synthetase found in the biosynthetic pathway. Antimicrob. Agents Chemother. 57 (2013) 2603–2612. [PMID: 23529730]
[EC 2.6.99.3 created 2013]
 
 
EC 2.8.5.1     
Accepted name: S-sulfo-L-cysteine synthase (3-phospho-L-serine-dependent)
Reaction: O-phospho-L-serine + thiosulfate = S-sulfo-L-cysteine + phosphate
Other name(s): cysK2 (gene name)
Systematic name: thiosulfate:3-phospho-L-serine thiosulfotransferase
Comments: The enzyme, which has been characterized from the bacterium Mycobacterium tuberculosis, has no activity with O-acetyl-L-serine. Requires pyridoxal 5′-phosphate. cf. EC 2.5.1.144, S-sulfo-L-cysteine synthase (O-acetyl-L-serine-dependent).
References:
1.  Steiner, E.M., Both, D., Lossl, P., Vilaplana, F., Schnell, R. and Schneider, G. CysK2 from Mycobacterium tuberculosis is an O-phospho-L-serine-dependent S-sulfocysteine synthase. J. Bacteriol. 196 (2014) 3410–3420. [PMID: 25022854]
[EC 2.8.5.1 created 2018]
 
 


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