Involved in the biosynthesis of the pterocarpin phytoalexins. Acts on isoflavones with a 4'-methoxy group on the B-ring, such as formononetin and biochanin A, and on pseudobaptigenin. Has a low activity with daidzein and genistein and no activity with the 7-O-methylated isoflavonoids isoformononetin and prunetin. formononetin + O2 + reduced [NADPH--hemoprotein reductase] = 2'-hydroxyformononetin + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] kcat is 0.015 sec(-1) with formononetin as substrate. kcat is 0.033 sec(-1) with biochanin A as substrate. Optimum pH is 8.0. Expressed constitutively in roots, but present at very low levels in uninfected stems and leaves. Down-regulated in roots by drought Up-regulated in leaves upon infection with fungus. No regulation by methyl jasmonate or elicitor treatment. Belongs to the cytochrome P450 family.