A novel procedure for the preparation and characterization of catalytically active fatty acid synthetase immobilized on sepharose beads.

A novel procedure for immobilization of enzymatically active fatty acid synthetase is presented. The enzyme is coupled to a Sepharose 4B matrix containing covalently attached antibodies which recognize, and bind specifically to, the thioesterase domain of this polyfunctional enzyme. A continuous flow system is described for assay of the immobilized enzyme. Fatty acid synthetase activity apparently is not limited by movement of substrates through the Nernst diffusion layer surrounding the matrix particles, since normal Michaelis-Menten kinetics are observed and reaction rates are independent of flow rate. The Km values for acetyl-CoA and malonyl-CoA, the pH/activity profile, and the reaction products are essentially the same as for the freely soluble enzyme, although the specific activity is lower by about 55%. The preparation and characterization of immobilized subunits of the enzyme could provide a valuable approach for studying the role of structural and functional subunit interactions in the enzyme. In addition, the immobilized enzyme offers a model for studying the properties of this enzyme in a highly structured environment such as might exist in vivo, permitting study of both physical and functional interactions of fatty acid synthetase with other lipogenic enzymes.