Rat, human, and chicken liver and yeast fatty acid synthetase complexes were dissociated into half-molecular weight nonidentical subunits of molecular weight 225,000-250,000 under the same conditions as used previously for the pigeon liver fatty acid synthetase complex [Lornitzo, F. A., Qureshi, A. A., and Porter, J. W. (1975) J. Biol. Chem. 250, 4520-45291. The separation of the half-molecular weight nonidentical subunits I and II of each fatty acid synthetase was then achieved by affinity chromatography on Sepharose epsilon-aminocaproyl pantetheine. The separations required, as with the pigeon liver fatty acid synthetase, a careful control of temperature, ionic strength, pH, and column flow rate for success, along with the freezing of the enzyme at -20C prior to the dissociation of the complex and the loading of the subunits onto the column. The separated subunit I (reductase) from each fatty acid synthetase contained beta-ketoacyl and crotonyl thioester reductases. Subunit II (transacylase) contained acetyl- and malonyl-coenzyme A: pantetheine transacylases. Each subunit of each complex also contained activities for the partial reactions, P-hydroxyacyl thioester dehydrase (crotonase), and palmitoyl-CoA deacylase. The specific activities of a given partial reaction did not vary in most cases more than twofold from one fatty acid synthetase species to another. The rat and human liver fatty acid synthetases required a much higher ionic strength for stability of their complexes and for the reconstitution of their overall synthetase activity from subunits I and II than did the pigeon liver enzyme. On reconstitution by dialysis in high ionic strength potassium phosphate buffer of subunits I and II of each complex, 65-85% of the control fatty acid synthetase activity was recovered. The rat and human liver fatty acid synthetases cross-reacted on immunoprecipitation with antisera. Similarly, chicken and pigeon liver fatty acid synthetases cross-reacted with their antisera. There was, however, no cross-reaction between the mammalian and avian liver fatty acid synthetases and the yeast fatty acid synthetase did not cross-react with any of the liver fatty acid synthetase antisera.

• PMID: 65153
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Reference Type

Comparative Study | Journal Article | Research Support, U.S. Gov't, P.H.S.

Authors

Qureshi AA, Lornitzo FA, Jenik RA, Porter JW

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