EFFECTS OF TRYPSIN ON ELECTRON TRANSPORT SYSTEMS OF LIVER MICROSOMES

Treatment of rat liver microsomes with low amounts of trypsin resulted in an inactivation of NADPH‐cytochrome P‐450 reductase parallel to the release of NADPH‐cytochrome c reductase. Associated herewith there was an inhibition of the NADPH‐linked drug hydroxylation and lipid peroxidation activities, as well as an inactivation of the reduction of cytochrome b5 by NADPH. The NADH‐cytochrome c reductase system, on the other hand, was considerably less sensitive to trypsin treatment of the microsomes. The inhibition of the NADH‐cytochrome c reductase activity at higher concentrations of trypsin was, however, likewise correlated with a solubilization of cytochrome b5. High concentrations of trypsin also caused a conversion of cytochrome P‐450 into cytochrome P‐420 and a disappearance of the spectral shift characteristic of the interaction of cytochrome P‐450 with substrates of the hydroxylating system. Copyright © 1969, Wiley Blackwell. All rights reserved