Identity of Malonyl and Palmitoyl Transferase of Fatty Acid Synthetase from Yeast. 2. A Comparison of Active-Site Peptides

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Abstract
Active-site peptides of malonyl and palmitoyl transferase from brewer''s yeast fatty acid synthetase were isolated and sequenced to try to prove the hypothesis that both enzymes are identical. For this purpose synthetase modified with 5,5''-dithiobis(2-nitrobenzoic acid) was labeled with either [14C]malonyl or [14C]palmitoyl residues followed by proteolytic digestion of the labeled protein. [14C]Malonyl-peptides were isolated by conventional purification procedures; their structures were determined by a combination of methods. [14C]Palmitoyl-peptide material was purified by high-performance liquid chromatography and the structure determined by solid-phase Edman degradation and other analytical methods. Serine was identified as the acyl acceptor group in both transferases. Comparison of the sequence data available shows that the sequence around the acyl acceptor group in both cases is identical. This proves the identity of malonyl and palmitoyl transferase.