6a-hydroxymaackiain

HI4 OMT from G. echinata is thought to be distinct from the M. sativa lOMT, because a separate daidzein 7-OMT is present in G. echinata, prompting the suggestion that the lOMT be renamed D70MT. The HI4 OMT amino acid sequence is closely related to that of the SAM (+)-6a-hydroxymaackiain 3-(9-methyltransferase (HM30MT), which carries out a similar reaction in (+)-pisatin biosynthesis in Pisum sativum (pea) (see Section 3.9.7). The... 

HI4 OMT protein showed activity against the 3-hydroxyl of a compound related to (+)-6a-hydroxymaackiain, ( + )-medicarpin, suggesting HM OMT may be functionally identical to HM30MT. However, the HM30MT substrate is only found in species making (+)-pisatin. The G. echinata HM OMT cDNA was used to isolate HM OMT cDNAs from L. japonicus, M. truncatula, and other legumes. Both HM OMT and lOMT may be involved in formono-netin biosynthesis, perhaps in the same tissues, and the formation of heterodimers of similar OMTs has been reported. 

Preisig, C. L., Matthews, D. E., VanEtten, H. D.,1989, Purification and characterization of S-adenosyl-L-methionine 6a-hydroxymaackiain 3-0-methyltransferase from Pisum sativum, Plant Physiol. 91 559-566. 

WU, Q., PREISIG, C.L., VANETTEN, H.D., Isolation of the cDNAs encoding (+)6a-hydroxymaackiain 3-O-methyltransferase, the terminal step for the biosynthesis of the phytoalexin pisatin in Pisum sativum L. Plant Mol. Biol., 1997, 35,551-560. 

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