6‐Methylsalicylic Acid Synthetase from Penicillium patulum

Abstract

1 The specificity of 6-methylsalicylic acid synthetase with respect to the priming substrate was studied. If acetyl-CoA was replaced by propionyl-CoA 6-ethylsalicylic acid was synthesized. The rate of this synthesis was about l3% that of 6-methylsalicylic acid synthesis in presence of acetyl-CoA. 2 6-Methylsalicylic acid synthetase contains an acetyl transferase activity as demonstrated by the transfer of acetyl residues from acetyl-CoA to pantetheine. This transferase also catalyses propionyl transfer but only with an about 13 times slower rate. 3 Analogous to fatty acid synthetase, treatment with iodoacetamide converts 6-methylsalicylic acid synthetase into a malonyl-CoA decarboxylase. Under certain conditions the iodoacetamide-treated enzyme could catalyse 6-methylsalicylic acid formation from malonyl CoA and NADPH without the external addition of acetyl CoA.