Cytochrome P450 monooxygenases of DIBOA biosynthesis: Specificity and conservation among grasses

DIBOA and DIMBOA are secondary metabolites of grasses which function as nat ural pestizides. The four maize gents BX2 through BX5 encode cytochrome P45 0-dependent monooxygenases that catalyse four consecutive reactions in the biosynthesis of these secondary products. Although BX2-BX5 share significan t sequence homology, the four enzymes have evolved into specific enzymes ea ch catalysing predominantly only one reaction in the pathway. In addition t o these natural reactions. BX3 hydroxylates 1.4-benzoxazin-3-one and BX2 sh ows pCMA demethylase activity. With respect to DIBOA biosynthesis. identica l enzymatic reactions have been found in rye as compared to maize, indicati ng early evolution of the P450 enzymes in the grasses. (C) 1999 Published b y Elsevier Science Ltd. All rights reserved.