Cerulenin resistance in a cerulenin-producing fungus. II. Characterization of fatty acid synthetase from Cephalosporium caerulens.
Cerulenin, an antifungal antibiotic isolated from a culture filtrate of Cephalosporium caerulens, is a potent inhibitor of fatty acid synthetase systems of various microorganisms and animal tissues. This antibiotic specifically blocks the activity of beta-ketoacyl thioester synthetase (condensing enzyme) by binding to the functional cysteine-SH in the active center of the condensing enzyme domain (the peripheral SH-group). However, fatty acid synthetase from C. caerulens is much less sensitive to cerulenin than fatty acid synthetases from other sources. The properties of C. caerulens synthetase were investigated and compared to those of Saccharomyces cerevisiae synthetase, which is sensitive to the antibiotic. The molecular weight of the enzymically active form of C. caerulens synthetase was 2.53 X 10(6). The enzyme consisted of two multifunctional proteins, alpha and beta, which are arranged in a complex, alpha 6 beta 6. The synthetase was inactivated by iodoacetamide. At 0 degrees C and pH 7.15, the second-order rate constant of k = 15.6 M-1 X s-1 was obtained for the inactivation by iodoacetamide. This value was about 15 times greater than that for S. cerevisiae synthetase. Treatment of C. caerulens synthetase with iodoacetamide, while impairing the synthetase activity, induced malonyl-CoA decarboxylase activity. When S. cerevisiae synthetase was preincubated with cerulenin, malonyl-CoA decarboxylase activity could not be detected even after treatment of the enzyme with iodoacetamide (Kawaguchi, A., Tomoda, H., Nozoe, S., Omura, S., & Okuda, S. (1982) J. Biochem. 92, 7-12). In the case of C. caerulens synthetase, on the other hand, malonyl-CoA decarboxylase activity was induced by iodoacetamide even after the preincubation of the enzyme with cerulenin.(ABSTRACT TRUNCATED AT 250 WORDS)
D000164:Acremonium / Q000201:enzymology*; D002262:Carboxy-Lyases / Q000302:isolation & purification / Q000378:metabolism; D002569:Cerulenin / Q000096:biosynthesis / Q000633:toxicity; D004351:Drug Resistance; D064429:Fatty Acid Synthases / Q000302:isolation & purification / Q000378:metabolism*; D007460:Iodoacetamide / Q000494:pharmacology; D046911:Macromolecular Substances; D008970:Molecular Weight; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D013045:Species Specificity
D046911:Macromolecular Substances; D002569:Cerulenin; D064429:Fatty Acid Synthases; D002262:Carboxy-Lyases; C021532:malonyl-CoA decarboxylase; D007460:Iodoacetamide