CYTOCHROME-P-450-CATALYZED MONOTERPENOID OXIDATION IN CATMINT (NEPETA-RACEMOSA) AND AVOCADO (PERSEA-AMERICANA) - EVIDENCE FOR RELATED ENZYMES WITH DIFFERENT ACTIVITIES

A cytochrome P-450 present in ripening avocado (Persea americana) fruit mesocarp (CYP71A1) had previously been shown to metabolize the monoterpenoids nerol and geraniol (Hallahan et al. (1992) Plant Physiol. 98, 1290-1297). Using DNA encoding CYP71A1 as a hybridization probe, we have shown by Southern analysis that a related gene is present in the catmint, Nepeta racemosa. RNA blot analysis, together with Western analysis of catmint leaf polypeptides using avocado cyt P-450 antiserum, showed that a closely related gene is expressed in catmint leaves. Cytochrome P-450 in catmint microsomes catalysed the specific hydroxylation of nerol and geraniol at C-10, whereas avocado CYP71A1, in either avocado microsomes or heterologously expressed in yeast, catalysed 2,3- or 6,7-epoxidation of these substrates. These results suggest that orthologous genes of the CYP71 family are expressed in these two plant species, but catalyse dissimilar reactions with monoterpenoid substrates.