Purification of the acyl coenzyme A reductase component from a complex responsible for the reduction of fatty acids in bioluminescent bacteria. Properties and acyltransferase activity.

The acyl-CoA reductase component of the fatty acid reductase complex responsible for synthesis of long chain aldehydes for the bioluminescent reaction in bacteria has been purified to homogeneity. The enzyme copurified as part of the complex through the initial steps and was then resolved and further purified to give a single band on sodium dodecyl sulfate-gel electrophoresis of molecular weight 58,000. The molecular weight of the native enzyme was 2 x 10(5), indicating it was an oligomeric enzyme containing identical subunits. The acyl-CoA reductase had a high specificity for NADPH with a Km value of 5 microM at optimal concentrations of tetradecanoyl-CoA (5-10 microM). The purified enzyme was discovered to have a high, intrinsic acyltransferase activity forming thioesters with a number of different thiol compounds (mercaptoethanol, dithiothreitol, 2-mercaptoethyl ether). The rates of the acyltransferase and acyl-CoA reductase reactions were similar to the rate of turnover of the fatty acid reductase complex suggesting that fatty acid reduction and not activation controls the rate of conversion of fatty acids to aldehydes.