Reaction: S-adenosyl-L-methionine + (+)-6a-hydroxymaackiain = S-adenosyl-L-homocysteine + (+)-pisatin
Glossary: (+)-6a-hydroxymaackiain = (6aR,12aR)-6H-[1,3]dioxolo[5,6][1]benzofuro[3,2-c]chromene-3,6a(12aH)-diol
(+)-pisatin = (6aR,12aR)-3-methoxy-6H-[1,3]dioxolo[5,6][1]benzofuro[3,2-c]chromen-6a(12aH)-ol
Other name(s): HM3OMT; HMM2
Systematic name: S-adenosyl-L-methionine:(+)-6a-hydroxymaackiain 3-O-methyltransferase
Comments: The protein from the plant Pisum sativum (garden pea) methylates (+)-6a-hydroxymaackiain at the 3-position. It also methylates 2,7,4'-trihydroxyisoflavanone on the 4'-position (cf. EC 2.1.1.212, 2,7,4-trihydroxyisoflavanone 4-O-methyltransferase) with lower activity.
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, CAS registry number:
References:
1. Preisig, C.L., Matthews, D.E. and Vanetten, H.D. Purification and characterization of S-adenosyl-L-methionine:6a-hydroxymaackiain 3-O-methyltransferase from Pisum sativum. Plant Physiol. 91 (1989) 559-566. [PMID: 16667069]
2. Wu, Q., Preisig, C.L. and VanEtten, H.D. Isolation of the cDNAs encoding (+)6a-hydroxymaackiain 3-O-methyltransferase, the terminal step for the synthesis of the phytoalexin pisatin in Pisum sativum. Plant Mol. Biol. 35 (1997) 551-560. [PMID: 9349277]
3. Liu, C.J., Deavours, B.E., Richard, S.B., Ferrer, J.L., Blount, J.W., Huhman, D., Dixon, R.A. and Noel, J.P. Structural basis for dual functionality of isoflavonoid O-methyltransferases in the evolution of plant defense responses. Plant Cell 18 (2006) 3656-3669. [PMID: 17172354]
4. Akashi, T., VanEtten, H.D., Sawada, Y., Wasmann, C.C., Uchiyama, H. and Ayabe, S. Catalytic specificity of pea O-methyltransferases suggests gene duplication for (+)-pisatin biosynthesis. Phytochemistry 67 (2006) 2525-2530. [PMID: 17067644]