[Oxidation of cytochrome b5 reduced by ascorbic acid].

The steady-state levels of aerobic and anaerobic reduction of cytochrome b5 by ascorbic acid and the initial rates of cytochrome b5 reduction in the presence of ascorbic acid and of anaerobic cytochrome P-450 reduction in the presence of NADH were used to calculate the rate constants for cytochrome b5 oxidation. The rate constant for cytochrome b5 autooxidation in the membrane is equal to that for isolated cytochrome b5, i. e.

[Reconstitution of the monooxygenase system in a solution and in an immobilized phospholipid layer].

To clarify the molecular organization of NADH- and NADPH-dependent microsomal redox systems their isolated purified carriers were incorporated into immobilized azolectin layer with a higher viscosity than that of the liposomes. It was shown that the NADH-cytochrome c reductase activity characterizing the NADH-cytochrome b5 reductase and cytochrome b5 interaction sharply decreased in the immobilized system as compared to that in solution. However, the activity of hydroxylase reactions catalyzed by immobilized NADPH-cytochrome P-450 reductase and cytochrome P-450 was the same as in solution.

[Effect of antioxidants of the 3-hydroxypyridine class on cyclic 3', 5'-adenosine monophosphate phosphodiesterase activity].

It was shown that derivatives of oxypyridine inhibit activity of 3,5-AMP phosphodiesterase I and II from the rabbit heart. 2-ethyl-6-methyl-3-oxypyridine and proxypheine inhibited 3,5-AMP phosphodiesterase activity in human lymphocytes substantially higher than theophilline widely used in clinical practice.

Characterization of two forms of cyclic nucelotide phosphodiesterase from rabbit heart.

Two forms of phosphodiesterase (PDE), one capable of being activated by calcium ions (PDE-I) and the other activated by cyclic nucelotides (PDE-II), were isolated from rabbit heart and separated by ion-exchange chromatography. PDE-I and PDE-II were shown to differ in molecular weight, kinetic constants, and in sensitivity to a number of chemical agents. Neither phosphodiesterase form could be "transformed" into the other one with acetone, alcohol, Lubrol, sulfhydryl reagents, or by changes in pH, ionic strength, by repeated freezing and thawing, or limited proteolysis.

[Two forms of cyclic nucleotide phosphodiesterase and Ca-dependent protein regulator from rabbit skeletal muscles].

In rabbit skeletal muscle extracts the activity of phosphodiesterase practically insensitive to the increase of Ca2+ concentration from 10(-8) M up to 10(-5) M. The Ca2+-dependent protein regulator is separated from phosphodiesterase at the stage of isolation and purification. The activity of phosphodiesterase devoid of the protein regulator is inhibited by Ca2+ (10(-5)--10(-3) M).