NADPH: BIOCHANIN A OXIDOREDUCTASE FROM THE FUNGUS FUSARIUM JAVANICUM

Article abstract of DOI:10.1016/S0031-9422(00)83862-5

A soluble enzyme which catalyses the NADPH-dependent reduction of the heterocyclic double bond of the isoflavone biochanin A (5,7-dihydroxy-4'-methoxy-isoflavone) yielding the corresponding isoflavanone was isolated from the fungus Fusarium javanicum.The NADPH: biochanin A oxidoreductase was constitutively present in the mycelium with an extractable average activity of 4 pkat/g fresh weight.The enzyme was purified ca 4500 fold to apparent homogeneity.The native enzyme had M_r of ca 87000 and consisted of two identical subunits of M_r 43000.The enzyme reaction showed a pH-optimum at pH 7.5 and a temperature optimum between 30 and 35 deg.The apparent K_m values were 43 μM for biochanin A and 190 μM for NADPH with a maximum velocity of 4 mkat/kg protein.The enzyme exhibited a remarkable substrate specificity for biochanin A. - Key Word Index: Fusarium javanicum; Hyphomycetes; NADPH: biochanin A oxidoreductase; isoflvone metabolism; biochanin A.