Reaction: (1) 2 S-adenosyl-L-methionine + tricetin = 2 S-adenosyl-L-homocysteine + 3',5'-O-dimethyltricetin
(1a) S-adenosyl-L-methionine + tricetin = S-adenosyl-L-homocysteine + 3'-O-methyltricetin
(1b) S-adenosyl-L-methionine + 3'-O-methyltricetin = S-adenosyl-L-homocysteine + 3',5'-O-dimethyltricetin
Glossary: tricin = 3',5'-O-dimethyltricetin
Other name(s): ROMT-17; ROMT-15; HvOMT1; ZmOMT1
Systematic name: S-adenosyl-L-methionine:tricetin 3',5'-O-dimethyltransferase
Comments: The enzymes from Oryza sativa (ROMT-15 and ROMT-17) catalyses the stepwise methylation of tricetin to its 3'-mono- and 3',5'-dimethyl ethers. In contrast with the wheat enzyme (EC 2.1.1.169, tricetin 3',4',5'-O-trimethyltransferase), tricetin dimethyl ether is not converted to its 3',4',5'-trimethylated ether derivative [1]. The enzymes from Hordeum vulgare (HvOMT1) and from Zea mays (ZmOMT1) form the 3',5'-dimethyl derivative as the major product [2].
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, CAS registry number:
References:
1. Lee, Y.J., Kim, B.G., Chong, Y., Lim, Y. and Ahn, J.H. Cation dependent O-methyltransferases from rice. Planta 227 (2008) 641-647. [PMID: 17943312]
2. Zhou, J.-M., Fukushi, Y., Wollenweber, E., Ibrahim, R.K. Characterization of two O-methyltransferase-like genes in barley and maize. Pharm. Biol. 46 (2008) 26-34.