The Enzyme Database

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EC 1.1.1.242      
Transferred entry: zeatin reductase. Now EC 1.3.1.69, zeatin reductase
[EC 1.1.1.242 created 1992, deleted 2001]
 
 
EC 1.3.1.69     
Accepted name: zeatin reductase
Reaction: dihydrozeatin + NADP+ = zeatin + NADPH + H+
Glossary: zeatin.html">zeatin = (E)-2-methyl-4-(9H-purin-6-ylamino)but-2-en-1-ol = (E)-N6-(4-hydroxy-3-methylbut-2-enyl)adenine
Systematic name: dihydrozeatin:NADP+ oxidoreductase
Comments: Previously classified erroneously as EC 1.1.1.242.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 123644-82-6
References:
1.  Martin, R.C., Mok, M.C., Shaw, G. and Mok, D.W.S. An enzyme mediating the conversion of zeatin to dihydrozeatin in Phaseolus embryos. Plant Physiol. 90 (1989) 1630–1635. [PMID: 16666974]
[EC 1.3.1.69 created 1992 as EC 1.1.1.242, transferred 2001 to EC 1.3.1.69]
 
 
EC 1.5.99.12     
Accepted name: cytokinin dehydrogenase
Reaction: N6-prenyladenine + acceptor + H2O = adenine + 3-methylbut-2-enal + reduced acceptor
Glossary: zeatin.html">zeatin = (E)-2-methyl-4-(9H-purin-6-ylamino)but-2-en-1-ol = (E)-N6-(4-hydroxy-3-methylbut-2-enyl)adenine
N6-prenyladenine = N6-(3-methylbut-2-en-1-yl)purin-6-amine
Other name(s): N6-dimethylallyladenine:(acceptor) oxidoreductase; 6-N-dimethylallyladenine:acceptor oxidoreductase; OsCKX2; CKX; cytokinin oxidase/dehydrogenase; N6-dimethylallyladenine:acceptor oxidoreductase
Systematic name: N6-prenyladenine:acceptor oxidoreductase
Comments: A flavoprotein (FAD). Catalyses the oxidation of cytokinins, a family of N6-substituted adenine derivatives that are plant hormones, where the substituent is a prenyl group. Although this activity was previously thought to be catalysed by a hydrogen-peroxide-forming oxidase, this enzyme does not require oxygen for activity and does not form hydrogen peroxide. 2,6-Dichloroindophenol, methylene blue, nitroblue tetrazolium, phenazine methosulfate and copper(II) in the presence of imidazole can act as acceptors. This enzyme plays a part in regulating rice-grain production, with lower levels of the enzyme resulting in enhanced grain production [2].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 55326-39-1
References:
1.  Galuszka, P., Frebort, I., Sebela, M., Jacobsen, S. and Pec, P. Cytokinin oxidase or dehydrogenase? Mechanism of cytokinin degradation in plants. Eur. J. Biochem. 268 (2001) 450–461. [DOI] [PMID: 11168382]
2.  Ashikari, M., Sakakibara, H., Lin, S., Yamamoto, T., Takashi, T., Nishimura, A., Angeles, E.R., Qian, Q., Kitano, H. and Matsuoka, M. Cytokinin oxidase regulates rice grain production. Science 309 (2005) 741–745. [DOI] [PMID: 15976269]
[EC 1.5.99.12 created 2001]
 
 
EC 1.14.99.69     
Accepted name: tRNA 2-(methylsulfanyl)-N6-isopentenyladenosine37 hydroxylase
Reaction: 2-(methylsulfanyl)-N6-prenyladenosine37 in tRNA + reduced acceptor + O2 = N6-[(2E)-4-hydroxy-3-methylbut-2-en-1-yl]-2-(methylsulfanyl)adenosine37 in tRNA + acceptor + H2O
Glossary: 2-(methylsulfanyl)-N6-prenyladenosine = N6-(3-methylbut-2-en-1-yl)-2-(methylsulfanyl)adenosine
Other name(s): miaE (gene name); tRNA 2-methylthio-N6-isopentenyl adenosine(37) hydroxylase; tRNA 2-(methylsulfanyl)-N6-dimethylallyladenosine37 hydroxylase
Systematic name: tRNA 2-(methylsulfanyl)-N6-prenyladenosine37,donor:oxygen 4-oxidoreductase (trans-hydroxylating)
Comments: The enzyme, found only within a small subset of facultative anaerobic bacteria, belongs to the nonheme diiron family. The enzyme from Salmonella typhimurium was shown to catalyse a stereoselective (E)-hydroxylation at the terminal C4-position of the prenyl group.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB
References:
1.  Persson, B.C. and Bjork, G.R. Isolation of the gene (miaE) encoding the hydroxylase involved in the synthesis of 2-methylthio-cis-ribozeatin in tRNA of Salmonella typhimurium and characterization of mutants. J. Bacteriol. 175 (1993) 7776–7785. [DOI] [PMID: 8253666]
2.  Persson, B.C., Olafsson, O., Lundgren, H.K., Hederstedt, L. and Bjork, G.R. The ms2io6A37 modification of tRNA in Salmonella typhimurium regulates growth on citric acid cycle intermediates. J. Bacteriol. 180 (1998) 3144–3151. [DOI] [PMID: 9620964]
3.  Corder, A.L., Subedi, B.P., Zhang, S., Dark, A.M., Foss, F.W., Jr. and Pierce, B.S. Peroxide-shunt substrate-specificity for the Salmonella typhimurium O2-dependent tRNA modifying monooxygenase (MiaE). Biochemistry 52 (2013) 6182–6196. [DOI] [PMID: 23906247]
[EC 1.14.99.69 created 2020]
 
 
EC 2.4.1.118     
Accepted name: cytokinin 7-β-glucosyltransferase
Reaction: UDP-glucose + an N6-alkylaminopurine = UDP + an N6-alkylaminopurine-7-β-D-glucoside
Glossary: zeatin.html">zeatin = (E)-2-methyl-4-(9H-purin-6-ylamino)but-2-en-1-ol = (E)-N6-(4-hydroxy-3-methylbut-2-enyl)adenine
Other name(s): uridine diphosphoglucose-zeatin 7-glucosyltransferase; cytokinin 7-glucosyltransferase; UDP-glucose:zeatin 7-glucosyltransferase
Systematic name: UDP-glucose:N6-alkylaminopurine 7-glucosyltransferase
Comments: Acts on a range of N6-substituted adenines, including zeatin and N6-benzylaminopurine, but not N6-benzyladenine. With some acceptors, 9-β-D-glucosides are also formed.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 72103-03-8
References:
1.  Entsch, B. and Letham, D.S. Enzymic glucosylation of the cytokinin, 6-benzylaminopurine. Plant Sci. Lett. 14 (1979) 205–212.
2.  Entsch, B., Parker, C.W., Letham, D.S. and Summons, R.E. Preparation and characterization, using high-performance liquid chromatography, of an enzyme forming glucosides of cytokinins. Biochim. Biophys. Acta 570 (1979) 124–139. [DOI] [PMID: 486500]
[EC 2.4.1.118 created 1984]
 
 
EC 2.4.1.203     
Accepted name: trans-zeatin O-β-D-glucosyltransferase
Reaction: UDP-glucose + trans-zeatin = UDP + O-β-D-glucosyl-trans-zeatin
Glossary: zeatin.html">zeatin = (E)-2-methyl-4-(9H-purin-6-ylamino)but-2-en-1-ol = (E)-N6-(4-hydroxy-3-methylbut-2-enyl)adenine
Other name(s): zeatin O-β-D-glucosyltransferase; uridine diphosphoglucose-zeatin O-glucosyltransferase; zeatin O-glucosyltransferase
Systematic name: UDP-glucose:trans-zeatin O-β-D-glucosyltransferase
Comments: Unlike EC 2.4.1.215, cis-zeatin O-β-D-glucosyltransferase, UDP-D-xylose can also act as donor (cf. EC 2.4.2.40, zeatin O-β-D-xylosyltransferase).
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 123644-76-8
References:
1.  Dixon, S.C., Martin, R.C., Mok, R.C., Shaw, G. and Mok, D.W.S. Zeatin glycosylation enzymes in Phaseolus - isolation of O-glucosyltransferase from Phaseolus lunatus and comparison to O-xylosyltransferase from P. vulgaris. Plant Physiol. 90 (1989) 1316–1321. [PMID: 16666929]
[EC 2.4.1.203 created 1992, modified 2001]
 
 
EC 2.4.1.204      
Transferred entry: zeatin O-β-D-xylosyltransferase. Now EC 2.4.2.40, zeatin O-β-D-xylosyltransferase
[EC 2.4.1.204 created 1992, deleted 2003]
 
 
EC 2.4.1.215     
Accepted name: cis-zeatin O-β-D-glucosyltransferase
Reaction: UDP-glucose + cis-zeatin = UDP + O-β-D-glucosyl-cis-zeatin
Glossary: zeatin.html">zeatin = (E)-2-methyl-4-(9H-purin-6-ylamino)but-2-en-1-ol = (E)-N6-(4-hydroxy-3-methylbut-2-enyl)adenine
Systematic name: UDP-glucose:cis-zeatin O-β-D-glucosyltransferase
Comments: The enzyme from maize can use cis-zeatin and UDP-glucose as substrates, but not cis-ribosylzeatin, trans-zeatin or trans-ribosylzeatin. Unlike EC 2.4.1.203, trans-zeatin O-β-D-glucosyltransferase, UDP-D-xylose cannot act as a donor.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 123644-76-8
References:
1.  Martin, R.C., Mok, M.C., Habben, J.E. and Mok, D.W.S. A maize cytokinin gene encoding an O-glucosyltransferase specific to cis-zeatin. Proc. Natl. Acad. Sci. USA 98 (2001) 5922–5926. [DOI] [PMID: 11331778]
[EC 2.4.1.215 created 2001]
 
 
EC 2.4.2.40     
Accepted name: zeatin O-β-D-xylosyltransferase
Reaction: UDP-D-xylose + zeatin = UDP + O-β-D-xylosylzeatin
Glossary: zeatin.html">zeatin = (E)-2-methyl-4-(9H-purin-6-ylamino)but-2-en-1-ol = (E)-N6-(4-hydroxy-3-methylbut-2-enyl)adenine
Other name(s): uridine diphosphoxylose-zeatin xylosyltransferase; zeatin O-xylosyltransferase
Systematic name: UDP-D-xylose:zeatin O-β-D-xylosyltransferase
Comments: Does not act on UDP-glucose (cf. EC 2.4.1.103 alizarin 2-β-glucosyltransferase).
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 110541-22-5
References:
1.  Turner, J.E., Mok, D.W.S., Mok, M.C. and Shaw, G. Isolation and partial-purification of an enzyme catalyzing the formation of O-xylosylzeatin in Phaseolus vulgaris embryos. Proc. Natl. Acad. Sci. USA 84 (1987) 3714–3717. [DOI] [PMID: 16593839]
[EC 2.4.2.40 created 1992 as EC 2.4.1.204, transferred 2003 to EC 2.4.2.40]
 
 
EC 2.5.1.50     
Accepted name: zeatin 9-aminocarboxyethyltransferase
Reaction: O-acetyl-L-serine + zeatin = lupinate + acetate
For diagram of reaction, click here
Glossary: lupinate = (S)-2-amino-3-{[(E)-4-hydroxy-3-methylbut-2-enylamino]purin-9-yl}propanoate
zeatin.html">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.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 88086-35-5
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 3.2.1.175     
Accepted name: β-D-glucopyranosyl abscisate β-glucosidase
Reaction: D-glucopyranosyl abscisate + H2O = D-glucose + abscisate
For diagram of abscisic-acid biosynthesis, click here
Other name(s): AtBG1; ABA-β-D-glucosidase; ABA-specific β-glucosidase; ABA-GE hydrolase; β-D-glucopyranosyl abscisate hydrolase
Systematic name: β-D-glucopyranosyl abscisate glucohydrolase
Comments: The enzyme hydrolzes the biologically inactive β-D-glucopyranosyl ester of abscisic acid to produce active abscisate. Abscisate is a phytohormone critical for plant growth, development and adaption to various stress conditions. The enzyme does not hydrolyse β-D-glucopyranosyl zeatin [1].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Lee, K.H., Piao, H.L., Kim, H.Y., Choi, S.M., Jiang, F., Hartung, W., Hwang, I., Kwak, J.M., Lee, I.J. and Hwang, I. Activation of glucosidase via stress-induced polymerization rapidly increases active pools of abscisic acid. Cell 126 (2006) 1109–1120. [DOI] [PMID: 16990135]
2.  Kato-Noguchi, H. and Tanaka, Y. Effect of ABA-β-D-glucopyranosyl ester and activity of ABA-β-D-glucosidase in Arabidopsis thaliana. J. Plant Physiol. 165 (2008) 788–790. [DOI] [PMID: 17923167]
3.  Dietz, K.J., Sauter, A., Wichert, K., Messdaghi, D. and Hartung, W. Extracellular β-glucosidase activity in barley involved in the hydrolysis of ABA glucose conjugate in leaves. J. Exp. Bot. 51 (2000) 937–944. [DOI] [PMID: 10948220]
[EC 3.2.1.175 created 2011]
 
 
EC 4.2.99.13      
Transferred entry: β-(9-cytokinin)-alanine synthase. Now EC 2.5.1.50, zeatin 9-aminocarboxyethyltransferase
[EC 4.2.99.13 created 1984, deleted 2002]
 
 


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