The Enzyme Database

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EC 4.2.3.33     
Accepted name: stemar-13-ene synthase
Reaction: 9α-copalyl diphosphate = stemar-13-ene + diphosphate
For diagram of the biosynthesis of diterpenoids from 9alpha-copalyl diphosphate, click here
Glossary: syn-copalyl diphosphate = 9α-copalyl diphosphate
Other name(s): OsDTC2; OsK8; OsKL8; OsKS8; stemarene synthase; syn-stemar-13-ene synthase
Systematic name: 9α-copalyl-diphosphate diphosphate-lyase (stemar-13-ene-forming)
Comments: This diterpene cyclase produces stemar-13-ene, a putative precursor of the rice phytoalexin oryzalexin S. Phytoalexins are diterpenoid secondary metabolites that are involved in the defense mechanism of the plant, and are produced in response to pathogen attack through the perception of elicitor signal molecules such as chitin oligosaccharide, or after exposure to UV irradiation.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Mohan, R.S., Yee, N.K., Coates, R.M., Ren, Y.Y., Stamenkovic, P., Mendez, I. and West, C.A. Biosynthesis of cyclic diterpene hydrocarbons in rice cell suspensions: conversion of 9,10-syn-labda-8(17),13-dienyl diphosphate to 9β-pimara-7,15-diene and stemar-13-ene. Arch. Biochem. Biophys. 330 (1996) 33–47. [DOI] [PMID: 8651702]
2.  Nemoto, T., Cho, E.M., Okada, A., Okada, K., Otomo, K., Kanno, Y., Toyomasu, T., Mitsuhashi, W., Sassa, T., Minami, E., Shibuya, N., Nishiyama, M., Nojiri, H. and Yamane, H. Stemar-13-ene synthase, a diterpene cyclase involved in the biosynthesis of the phytoalexin oryzalexin S in rice. FEBS Lett. 571 (2004) 182–186. [DOI] [PMID: 15280039]
[EC 4.2.3.33 created 2008]
 
 
EC 4.2.3.34     
Accepted name: stemod-13(17)-ene synthase
Reaction: 9α-copalyl diphosphate = stemod-13(17)-ene + diphosphate
For diagram of the biosynthesis of diterpenoids from 9alpha-copalyl diphosphate, click here
Glossary: syn-copalyl diphosphate = 9α-copalyl diphosphate
exo-stemodene = stemod-13(17)-ene
Other name(s): OsKSL11; stemodene synthase
Systematic name: 9α-copalyl-diphosphate diphosphate-lyase [stemod-13(17)-ene-forming]
Comments: This enzyme catalyses the committed step in the biosynthesis of the stemodane family of diterpenoid secondary metabolites, some of which possess mild antiviral activity. The enzyme also produces stemod-12-ene and stemar-13-ene as minor products.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Morrone, D., Jin, Y., Xu, M., Choi, S.Y., Coates, R.M. and Peters, R.J. An unexpected diterpene cyclase from rice: functional identification of a stemodene synthase. Arch. Biochem. Biophys. 448 (2006) 133–140. [DOI] [PMID: 16256063]
[EC 4.2.3.34 created 2008]
 
 
EC 4.2.3.35     
Accepted name: syn-pimara-7,15-diene synthase
Reaction: 9α-copalyl diphosphate = 9β-pimara-7,15-diene + diphosphate
For diagram of the biosynthesis of diterpenoids from 9alpha-copalyl diphosphate, click here
Glossary: syn-copalyl diphosphate = 9α-copalyl diphosphate
syn-pimara-7,15-diene = 9β-pimara-7,15-diene
Other name(s): 9β-pimara-7,15-diene synthase; OsDTS2; OsKS4
Systematic name: 9α-copalyl-diphosphate diphosphate-lyase (9β-pimara-7,15-diene-forming)
Comments: This enzyme is a class I terpene synthase [1]. 9β-Pimara-7,15-diene is a precursor of momilactones A and B, rice diterpenoid phytoalexins that are produced in response to attack (by a pathogen, elicitor or UV irradiation) and are involved in the defense mechanism of the plant. Momilactone B can also act as an allochemical, being constitutively produced in the root of the plant and secreted to the rhizosphere where it suppresses the growth of neighbouring plants and soil microorganisms [1].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Wilderman, P.R., Xu, M., Jin, Y., Coates, R.M. and Peters, R.J. Identification of syn-pimara-7,15-diene synthase reveals functional clustering of terpene synthases involved in rice phytoalexin/allelochemical biosynthesis. Plant Physiol. 135 (2004) 2098–2105. [DOI] [PMID: 15299118]
2.  Otomo, K., Kanno, Y., Motegi, A., Kenmoku, H., Yamane, H., Mitsuhashi, W., Oikawa, H., Toshima, H., Itoh, H., Matsuoka, M., Sassa, T. and Toyomasu, T. Diterpene cyclases responsible for the biosynthesis of phytoalexins, momilactones A, B, and oryzalexins A-F in rice. Biosci. Biotechnol. Biochem. 68 (2004) 2001–2006. [DOI] [PMID: 15388982]
[EC 4.2.3.35 created 2008]
 
 
EC 4.2.3.42     
Accepted name: aphidicolan-16β-ol synthase
Reaction: 9α-copalyl diphosphate + H2O = aphidicolan-16β-ol + diphosphate
For diagram of diterpenoid biosynthesis, click here and for reaction mechanism, click here
Other name(s): PbACS
Systematic name: 9α-copalyl-diphosphate diphosphate-lyase (aphidicolan-16β-ol-forming)
Comments: This is a bifunctional enzyme which also has EC 5.5.1.14 syn-copalyl diphosphate synthase activity. Aphidicolan-16β-ol is a precursor of aphidicolin, a specific inhibitor of DNA polymerase α (EC 2.7.7.7).
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Oikawa, H., Toyomasu, T., Toshima, H., Ohashi, S., Kawaide, H., Kamiya, Y., Ohtsuka, M., Shinoda, S., Mitsuhashi, W. and Sassa, T. Cloning and functional expression of cDNA encoding aphidicolan-16 β-ol synthase: a key enzyme responsible for formation of an unusual diterpene skeleton in biosynthesis of aphidicolin. J. Am. Chem. Soc. 123 (2001) 5154–5155. [PMID: 11457369]
2.  Toyomasu, T., Nakaminami, K., Toshima, H., Mie, T., Watanabe, K., Ito, H., Matsui, H., Mitsuhashi, W., Sassa, T. and Oikawa, H. Cloning of a gene cluster responsible for the biosynthesis of diterpene aphidicolin, a specific inhibitor of DNA polymerase α. Biosci. Biotechnol. Biochem. 68 (2004) 146–152. [DOI] [PMID: 14745177]
[EC 4.2.3.42 created 2009]
 
 
EC 4.2.3.99     
Accepted name: labdatriene synthase
Reaction: 9α-copalyl diphosphate = (12E)-9α-labda-8(17),12,14-triene + diphosphate
For diagram of diterpenoids from 9α-copalyl diphosphate, click here
Glossary: 9α-copalyl diphosphate = syn-copalyl diphosphate = (2E)-3-methyl-5-[(1R,4aS,8aS)-5,5,8a-trimethyl-2-methylidenedecahydronaphthalen-1-yl]pent-2-en-1-yl trihydrogen diphosphate
(12E)-9α-labda-8(17),12,14-triene = (4aS,5R,8aS)-1,1,4a-trimethyl-6-methylidene-5-[(2E)-3-methylpenta-2,4-dien-1-yl]decahydronaphthalene
Other name(s): OsKSL10 (gene name)
Systematic name: 9α-copalyl-diphosphate diphosphate-lyase [(12E)-9α-labda-8(17),12,14-triene-forming]
Comments: The enzyme from rice (Oryza sativa), expressed in Escherichia coli, also produces ent-sandaracopimara-8(14),15-diene from ent-copalyl diphosphate, another naturally occuring copalyl isomer in rice (cf. ent-sandaracopimaradiene synthase, EC 4.2.3.29).
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Morrone, D., Hillwig, M.L., Mead, M.E., Lowry, L., Fulton, D.B. and Peters, R.J. Evident and latent plasticity across the rice diterpene synthase family with potential implications for the evolution of diterpenoid metabolism in the cereals. Biochem. J. 435 (2011) 589–595. [DOI] [PMID: 21323642]
[EC 4.2.3.99 created 2012]
 
 
EC 5.5.1.14     
Accepted name: syn-copalyl-diphosphate synthase
Reaction: geranylgeranyl diphosphate = 9α-copalyl diphosphate
For diagram of diterpenoids from 9α-copalyl diphosphate, click here
Glossary: syn-copalyl diphosphate = 9α-copalyl diphosphate
Other name(s): OsCyc1; OsCPSsyn; syn-CPP synthase; syn-copalyl diphosphate synthase; 9α-copalyl-diphosphate lyase (decyclizing)
Systematic name: 9α-copalyl-diphosphate lyase (ring-opening)
Comments: Requires a divalent metal ion, preferably Mg2+, for activity. This class II terpene synthase produces syn-copalyl diphosphate, a precursor of several rice phytoalexins, including oryzalexin S and momilactones A and B. Phytoalexins are diterpenoid secondary metabolites that are involved in the defense mechanism of the plant, and are produced in response to pathogen attack through the perception of elicitor signal molecules such as chitin oligosaccharide, or after exposure to UV irradiation. The enzyme is constitutively expressed in the roots of plants where one of its products, momilactone B, acts as an allelochemical (a molecule released into the environment to suppress the growth of neighbouring plants). In other tissues the enzyme is upregulated by conditions that stimulate the biosynthesis of phytoalexins.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Otomo, K., Kenmoku, H., Oikawa, H., Konig, W.A., Toshima, H., Mitsuhashi, W., Yamane, H., Sassa, T. and Toyomasu, T. Biological functions of ent- and syn-copalyl diphosphate synthases in rice: key enzymes for the branch point of gibberellin and phytoalexin biosynthesis. Plant J. 39 (2004) 886–893. [DOI] [PMID: 15341631]
2.  Xu, M., Hillwig, M.L., Prisic, S., Coates, R.M. and Peters, R.J. Functional identification of rice syn-copalyl diphosphate synthase and its role in initiating biosynthesis of diterpenoid phytoalexin/allelopathic natural products. Plant J. 39 (2004) 309–318. [DOI] [PMID: 15255861]
[EC 5.5.1.14 created 2008]
 
 


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