Identity of Malonyl and Palmitoyl Transferase of Fatty Acid Synthetase from Yeast. 1. Functional Interrelationships between the Acyl Transferases

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Abstract
Functional interrelationships between the acyl transferases of brewer''s yeast fatty acid synthetase were investigated. In binding assays with synthetase modified by 5,5''-dithiobis(2-nitrobenzoic acid), 4-5 malonyl transferase entities per multienzyme complex molecule could be titrated. In the presence of palmitoyl-CoA these malonyl transferases were inaccessible to malonyl-CoA, whereas the acetyl transferases were reactive towards acetyl-CoA. Between 4 and 5 palmitoyl transferase entities per synthetase equivalent were found reactive towards palmitoyl-CoA, the palmitoyl binding being inhibited by malonyl-CoA. Following palmitoyl binding the acetyl transferases were reactive towards acetyl-CoA. Substrate model assays were consistent with these data. Malonyl and palmitoyl transferases are closely coupled enzyme components of the multienzyme complex which are farly independent of the acetyl transferase entities. The molecular basis for the observed coupling will be given.