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A A Akhrem

Publications and source records attributed to A A Akhrem.

At least 127 records · Page 7Linked to original sources
PubMed1978

[Effect of phase transitions in microsomal membranes on energetic characteristics of oxidation].

Naphthalene and aniline oxidation by intact and induced enzyme systems of rat liver microsomes, NADPH and O2 has been studied in a broad temperature range. The oxidation of the same substrates has also been studied in the systems "microsomes--cumene hydroperoxide" and "purified cytochrome P-450--cumene hydroperoxide". The temperature curves of catalytic constants for type I substrate (naphthalene-oxidation) in the system with cofactors is characterized by break on Arrenius dependence near 18--24 degrees C and explained by phase transitions of microsomal membrane lipids. The temperature curves of catalytic constants for type II substrate (aniline-oxidation) in all studied systems do not break on Arrenius plots. Catalytic oxidation contants of both substrates in systems "microsomes--hydroperoxide" and "cytochrome P-450--hydroperoxide" are characterized by constant activation energies in broad temperature range. The results obtained are discussed from the point of view of the effect of phospholipids phase transitions in microsomal membrane on a rate limiting step.

Aniline Compounds↗
PubMed1977

The nature of the rate-limiting step in aniline hydroxylation involving cytochrome p-450 rat liver microsomes.

The kinetics of aniline hydroxylation was studied with: (1) rat liver microsomes involving NADPH and O2 (system 1), (2) hepatic microsomes and tert-butylhydroperoxide (system 2) and (3) microsomes and cumyl hydroperoxide (system 3) at 15--37 degrees C. The reactions were characterized by the values of the aniline oxidation rate constants, k2 = V/E0, where E0 is the initial concentration of cytochrome P-450: K 1/2 = 1.60 - 10(8) EXP (-13 400/RT) sec-1, k 2/2 = 1.66 - 10(9) exp (-14 500/RT) sec-1, k 3/2 = 6.83 - 10(9) exp (-15 300/RT) sec-1. The values of delta H0 and delta S0, were calculated and compared for the three systems. The evidence suggests that oxygen insertion into the substrate molecule is the rate-limiting step in the reaction of aniline oxidation for the mentioned systems. The nature of aniline binding to cytochrome P-450 and that of the hydroxylating agent have been discussed.

Aniline Compounds↗
PubMed1977

[O-demethylation kinetics of anisole and p-chloroanisole by cumene hydroperoxide and cytochrome P-450 of liver microsomes].

The kinetics of anisole oxidation by microsomes and tertiary butylhydroperoxide have been studied in phosphate buffer (pH 7,4) at 37 degrees C. About 20% of the substrate are shown to undergo demetylation and about 80% were hydroxylated in the p-position. The kinetics of the oxidative o-demethylation of anisole and p-chloroanisole by cumene hydroperoxide and hepatic microsomes has been studied within the temperature range of 20--37 degrees C. The catalytic rate constants for o-demethylation of anisole and chloroanisole have been determined in a general form to equal 2,04.10(7) exp (--11400/RT) and 5,5.10(7) exp (--11800/RT) sec-1, respectively. The reactions of o-demethylation and hydroperoxide have been proved to be independent. The data obtained are indicative of the electrophilic nature of the hydroxylating agent in the system "microsomes-hydroperoxide".

Animals↗
PubMed1977

[The nature of the rate-limiting step in aniline hydroxylation involving cytochrome P-450 from rat liver microsomes].

The kinetics of aniline hydroxylation with: 1) rat liver microsomes involving NADPH and O2 (System I); 2) hepatic microsomes and tertiary butylhydroperoxide (System II) and 3) microsomes and cumyl hydroperoxide (System III) within 15--37 degrees C has been studied. The reactions were characterized by the values of the aniline oxidation rate constants, k2=v/[E]0, where [E]0 is the initial concentration of cytochrome P--450: k1 2=1,60.10(8) exp (--13400/RT) sec-1., k2 2=1,66.10(9) exp (--14500/RT) sec-1., k3 2=6,83.10(9) exp (--15300/RT) sec-1. The values of delta H* and delta S* were calculated and compared for these three systems. A conclusion is drawn that the act of oxygen insertion into the substrate molecule is the rate-limiting step in the reaction of aniline oxidation for the mentioned system.

Aniline Hydroxylase↗
PubMed1977

[Effect of temperature on the interaction of cytochrome P-450 with a variety of amines].

The interaction of cytochrome P-450 of rat liver microsomes with six amines have been investigated in Tris-HCL buffer pH 7.4 within the temperature range of 20--37 degrees C by the differential spectrophotometry method. Dissociation constants for the amine-cytochrome-P-450 complexes have been determined. The interaction of type I substrate, 1,2,7-trimethyl-decahydroquinolone-4, is characterized by the value of Ks(I)=4.14 exp (--6250/RT) mole/1. A value of Ks(II)=10(-8) exp (+6500/RT) mole/1 has been obtained for type II substrate, monomethylaniline. Association of 1,2,7-trimethyldecahydroquinolone-4 to cytochrome P-450 decreases with temperature, where as with monomethylaniline the reverse tendency is observed. Thermodynamic parameters delta H, delta F and delta S characterising the interaction of amines with cytochrome P-450 are evaluated.

Amines↗