The enzyme from the rice bean Vigna umbellata (Fabaceae) is highly specific for S-adenosyl-L-methionine. The enzyme also methylates 1L-1,2,4/3,5-cyclohexanepentol, 2,4,6/3,5-pentahydroxycyclohexanone, D,L-2,3,4,6/5-pentacyclohexanone and 2,2'-anhydro-2-C-hydroxymethyl-myo-inositol, but at lower rates than that of myo-inositol.