HYDROCARBON BIOSYNTHESIS IN THE HOUSE-FLY, MUSCA-DOMESTICA - SUBSTRATE-SPECIFICITY AND COFACTOR REQUIREMENT OF P450HYD

A study of the substrate specificity and transfer of electrons for the conversion of very long fatty acyl-CoA to hydrocarbon and CO2 by a cy tochrome P450 (P450hyd) type enzyme in microsomal preparations from ab dominal epidermal tissue of the house fly, Musca domestica, showed tha t the enzyme which converts alelehyde to hydrocarbon contributes littl e to the chain length of the hydrocarbon products observed in vivo. NA DPH (and not NADH) was required for the reduction of the fatty acyl-Co A to the corresponding aldehyde, and when both cofactors were added to gether, the amount of hydrocarbon formed from the acyl-CoA derivative was about the same as with NADPH alone, Both NADPH and NADH (less effe ctively) supported the conversion of the aldehyde to hydrocarbon and C O2 by P450hyd. When both pyridine nucleotides were added together with the aldehyde substrate, conversion to hydrocarbon was intermediate be tween the levels formed with either cofactor alone, suggesting that th e same electron carrier was transferring electrons from both NADH and NADPH and that cytochrome b(5) does not participate in the reaction, A ntibody to house By cytochrome P450 reductase inhibited the reaction w hen either NADPH or NADH was used, In addition, both NADP(+) and 2-AMP stimulated, rather than inhibited, hydrocarbon production in microsom es from female houseflies, presumably by inhibiting competing P450 enz ymes which are supplied with electrons by the NADPH-cytochrome P450 re ductase. These data suggest a novel mode of electron transfer to the P 450hyd.