Molecular Pharmacology, Vol 11, 809-817, Copyright © 1975 by the American Society for Pharmacology and Experimental Therapeutics

Characteristics of a Microsomal Dechlorination System

¹ Department of Anesthesiology, Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55901

Microsomes were solubilized and the components of the mixed-function oxidase system were isolated. With a reconstituted system containing partially purified cytochrome P-450, NADPH—cytochrome c reductase, NADPH, and phospholipid, dechlorination of 1,1,2-trichloroethane was observed. Addition of cytochrome b₅, NADH—cytochrome b₅ reductase, and cyanide-sensitive factor to this system resulted in additional activity, but the cytochrome b5 system by itself would not dechlorinate. The activity of the complete system was not altered by the presence of the cyanide-sensitive factor. Whole microsomes also were studied and the kinetics of the dechlorination reaction was determined. The K_m was 3.32 mM; V_max was 1.09 nmoles of substrate dechlorinated per minute per milligram of protein. The addition of NADH to the NADPH system significantly increased both K_m and V_max. The microsomal enzyme system required molecular oxygen; the presence of the cell supernatant fraction produced an increase in the V_max of dechlorination.

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ACKNOWLEDGMENT The authors are indebted to Mrs. Rita M. Nelson for her skillful technical assistance.