GENISTEIN AS AN ENDOGENOUS NATURAL SUBSTRATE OF ACIDIC PEROXIDASES INLUPIN HYPOCOTYLS

The localisation of peroxidase in the outermost cell layers of lupin ( Lupinus albus L. cv. Multolupa) hypocotyls shows that peroxidase activ ity is present mainly in the epidermal cell layer in a similar way to isoflavones. The soluble peroxidase activity is due mainly to the pres ence of two peroxidase isoenzyme groups, one of an acidic nature (A(1) and A(2)) and the other basic (B-1 and B-2). These isoenzymes, althou gh present in epidermal tissues, are not tissue-specific since they ar e also located in the soluble peroxidase fraction obtained from vascul ar tissues. These observations, and the fact that acidic peroxidases b ut not basic peroxidases are extremely active in the oxidation of geni stein, a constitutive isoflavone of lupin hypocotyls, point to a role for acidic peroxidases in isoflavone turnover and degradation. Thus, m anipulating peroxidase activity and/or its level would allow endogenou s isoflavone levels to be controlled in order to grow lupins as a comm ercial fodder crop.