KINETIC-STUDIES ON DELTA-5 DESATURASE SYSTEM IN RAT TESTICULAR AND HEPATIC MICROSOMES

Kinetics of and optimal conditions for the Delta 5 desaturase from tes tis were characterized for comparison with the liver enzyme. [7-C-14]8 , 11, 14-Eicosatrienoate was used as substrate and reaction rates were quantitated by gas-liquid radiochromatography. Initial velocities wer e linear with respect to lime (0-10 min.) and protein (0-5 mg). They w ere also coenzyme A (less than or equal to 0.1 mM), NADH (less than or equal to 1.5 mM), and temperature-dependent, and showed pH optima of 8.5 (testis) and 7.0 - 7.5 (liver). The Vm's were 0.13 and 0.39 respec tively and the Km's were both 14 mu M. Washed-microsome reconstitution revealed an enzymic requirement for soluble factors. Microsomal fatty -acid composition and fluorescence-polarization anisotropy with diphen ylhexatriene were measured and the unsaturation index calculated.