[Effect of thiol reagents on the activity of NADP-dependent malate dehydrogenase isolated from bovine adrenal cortex cytoplasm].
NADP-dependent malate dehydrogenase was rapidly inactivated in the presence of mercurous chloride. Titration of malate dehydrogenase by 5,5'-dithiobis (2-nitrobenzoic acid) (DTNB) in a solution of 8 M urea revealed 18 SH groups per molecule of the enzyme. Eight sulphydryl groups reacted with DTNB in native malate dehydrogenase and their modification was not accompanied by a loss of the enzyme activity. The interaction of p-chloromercury benzoate (PCMB) with malate dehydrogenase resulted in a 70% decrease in the enzyme activity. The binding of the thiol reagents by the malate dehydrogenase molecule appreciably increased the Michaelis constant value for the substrate. In the presence of magnesium ions, NADP and malate did not affect the process of malate dehydrogenase modification by DTNB and did not protect the enzyme from the inactivation by PCMB. It is suggested from the data obtained that the sulphyryl groups are involved in maintaining the active conformation of the enzyme.
S B
SB
Senkevich
S A
SA
Strumilo
V V
VV
Vinogradov
D000302:Adrenal Cortex / Q000201:enzymology*; D000818:Animals; D002417:Cattle; D003593:Cytoplasm / Q000201:enzymology; D004228:Dithionitrobenzoic Acid / Q000494:pharmacology; D066298:In Vitro Techniques; D008291:Malate Dehydrogenase / Q000037:antagonists & inhibitors* / Q000302:isolation & purification; D050538:Malate Dehydrogenase (NADP+); D011487:Protein Conformation; D013379:Substrate Specificity; D013438:Sulfhydryl Compounds / Q000032:analysis; D013439:Sulfhydryl Reagents / Q000494:pharmacology*
D013438:Sulfhydryl Compounds; D013439:Sulfhydryl Reagents; D004228:Dithionitrobenzoic Acid; D008291:Malate Dehydrogenase; D050538:Malate Dehydrogenase (NADP+)
Vliianie tiolovykh reagentov na aktivnost' NADP-zavisimoĭ malatdegidrogenazy, vydelennoĭ iz tsitoplazmy kory nadpochechnikov byka.