MECHANISM OF ACTION OF THE LACTIC DEHYDROGENASE OF THE MAMMALIAN ERYTHROCYTE: I. INFLUENCE OF INHIBITORS

1958 ◽  
Vol 36 (10) ◽  
pp. 1075-1083 ◽  
Author(s):  
Paul Ottolenghi ◽  
Orville F. Denstedt
Keyword(s):  
Mechanism Of Action ◽  
Lactic Dehydrogenase ◽  
Noncompetitive Inhibition ◽  
Mammalian Erythrocyte ◽  
Lactate And Pyruvate

This paper pertains to the inhibition of lactic dehydrogenase by substances structurally related to its substrates, pyruvate and lactate. Oxalate, tartronate, and malonate inhibit the enzyme in a competitive manner towards lactate, and in a noncompetitive manner towards pyruvate. Phenoxyacetate causes simultaneous competitive and noncompetitive inhibition towards both lactate and pyruvate. The results obtained lead to the conclusion that, for their activation, pyruvate and lactate react with different sites on the enzyme surface.

MECHANISM OF ACTION OF THE LACTIC DEHYDROGENASE OF THE MAMMALIAN ERYTHROCYTE: I. INFLUENCE OF INHIBITORS

1958 ◽  
Vol 36 (1) ◽  
pp. 1075-1083 ◽  
Author(s):  
Paul Ottolenghi ◽  
Orville F. Denstedt
Keyword(s):  
Mechanism Of Action ◽  
Lactic Dehydrogenase ◽  
Noncompetitive Inhibition ◽  
Mammalian Erythrocyte ◽  
Lactate And Pyruvate

This paper pertains to the inhibition of lactic dehydrogenase by substances structurally related to its substrates, pyruvate and lactate. Oxalate, tartronate, and malonate inhibit the enzyme in a competitive manner towards lactate, and in a noncompetitive manner towards pyruvate. Phenoxyacetate causes simultaneous competitive and noncompetitive inhibition towards both lactate and pyruvate. The results obtained lead to the conclusion that, for their activation, pyruvate and lactate react with different sites on the enzyme surface.

MECHANISM OF ACTION OF THE LACTIC DEHYDROGENASE OF THE MAMMALIAN ERYTHROCYTE: II. THE MECHANISM OF SUBSTRATE INHIBITION

1958 ◽  
Vol 36 (10) ◽  
pp. 1085-1091 ◽  
Author(s):  
Paul Ottolenghi ◽  
Orville F. Denstedt
Keyword(s):  
Mechanism Of Action ◽  
Substrate Inhibition ◽  
Lactic Dehydrogenase ◽  
Mammalian Erythrocyte

The inhibition of lactic dehydrogenase produced by an excess of the substrate pyruvate has been shown to be of the noncompetitive type. Thus, two sites on the enzyme appear to be involved: one for the activation of pyruvate, and a second one which, when complexed with a molecule of pyruvate, renders the enzyme inactive.

MECHANISM OF ACTION OF THE LACTIC DEHYDROGENASE OF THE MAMMALIAN ERYTHROCYTE: II. THE MECHANISM OF SUBSTRATE INHIBITION

1958 ◽  
Vol 36 (1) ◽  
pp. 1085-1091 ◽  
Author(s):  
Paul Ottolenghi ◽  
Orville F. Denstedt
Keyword(s):  
Mechanism Of Action ◽  
Substrate Inhibition ◽  
Lactic Dehydrogenase ◽  
Mammalian Erythrocyte

The inhibition of lactic dehydrogenase produced by an excess of the substrate pyruvate has been shown to be of the noncompetitive type. Thus, two sites on the enzyme appear to be involved: one for the activation of pyruvate, and a second one which, when complexed with a molecule of pyruvate, renders the enzyme inactive.

LACTIC DEHYDROGENASE OF THE MAMMALIAN ERYTHROCYTE: III. THE FORMATION OF A COMPLEX OF THE ENZYME WITH DPN AND LACTATE

1958 ◽  
Vol 36 (1) ◽  
pp. 1093-1098 ◽  
Author(s):  
Paul Ottolenghi ◽  
Orville F. Denstedt
Keyword(s):  
Ternary Complex ◽  
Kinetic Studies ◽  
Lactic Dehydrogenase ◽  
Binary Complex ◽  
Hydrogen Ions ◽  
Mammalian Erythrocyte

In the transfer of hydrogen ions and electrons from lactate to DPN by lactic dehydrogenase the lactate is capable of forming a complex only with the binary complex of enzyme and coenzyme to form an active ternary complex. The results of kinetic studies indicate that the site for the binding of lactate is on the DPN molecule itself.

Effects of pregnancy and lactation in sheep on the metabolism of propionate by the ruminal mucosa and on some enzymic activities in the ruminal mucosa

1972 ◽  
Vol 79 (3) ◽  
pp. 409-421 ◽  
Author(s):  
T. E. C. Weekes
Keyword(s):  
Alanine Aminotransferase ◽  
Dry Weight ◽  
Lactic Dehydrogenase ◽  
Total Weight ◽  
Unit Weight ◽  
Malic Dehydrogenase ◽  
Glutamic Dehydrogenase ◽  
Pregnancy And Lactation ◽  
Lactate And Pyruvate

SUMMARYRuminal papillae were removed at slaughter from pregnant, lactating and nonbreeding control ewes. The amounts of lactate and pyruvate formed per unit dry weight of papillae during incubation in vitrowith added propionate were not significantly affected by breeding state.When results were expressed relative to the total weight of mueosa in the rumen, the amounts of lactate and pyruvate formed were significantly greater for ewes slaughtered during the final two thirds of a 10-week period of lactation in comparison with unmated ewes slaughtered at the same time.The calculated extent of conversion of propionate absorbed from the rumen into lactate and pyruvate was small, averaging 3·0%.When results were expressed per unit weight of mucosa, breeding state did not significantly affect the activity of four of the enzymes involved in the conversion of propionate into lactate and pyruvate, namely propionyl-CoA synthetase, propionyl-CoA carboxylase, NADP-malic dehydrogenase and lactic dehydrogenase, or of aspartate aminotransferase.When results were expressed relative to the total weight of ruminal mucosa, the activities of all these enzymes and also of alanine aminotransferase were significantly greater during lactation than in control sheep slaughtered at the same time. The activities in ewes slaughtered during the last 50 days of pregnancy, however, were not significantly different from the control values.Glutamic dehydrogenase activity per unit weight of tissue was higher after the lambs had been weaned than during lactation. Alanine aminotransferase activity per unit weight of mucosa decreased during the last 50 days of pregnancy.

THE INFLUENCE OF SOME HYPOTENSIVE DRUGS ON THE SEROTONERGIC MECHANISMS IN RATS PLATELETS

1987 ◽  
Author(s):  
W Buczko ◽  
M Pietraszek ◽  
E Chabielska ◽  
B Malinowska
Keyword(s):  
Platelet Aggregation ◽  
Mechanism Of Action ◽  
Blood Platelets ◽  
Mechanisms Of Action ◽  
Noncompetitive Inhibition ◽  
Amine Uptake ◽  
Secondary Mechanism ◽  
Therapy Of Hypertension

Serotonin (5HT) is a vasoactive amine that has been reported to be involved in a number of forms of circulatory failure. The 5HT content and metabolism in platelets is changed in hypertension and in peripheral arteriolar diseases. The present study concerns the effect of verapamil (VER), propranolol (PRO) and cap-topril (CAP) - drugs having different hypotensive mechanisms of action, on serotonergic mechanisms in rat blood platelets. In vitro, VER produced noncompetitive inhibition of 14C-5HT uptake (IC50=8.2μM), PRO inhibited the uptake in a competitive fashion (Km =0.9μM), whereas CAP was ineffective. Only PRO released (24%) radioactive 5HT from incubated platelets. Inhibition of amine uptake was also obtained when plateletswere prepared from-irats pretreated with VER (10 mg.kg−1 ), PRO (5 mg.kg−1) or CAP (10 mg.kg−1 ). Moreover, the concentration of endogenous 5HT in blood platelets was reduced after VER and PRO administration. Platelets aggregation induced by ADP was inhibited by VER and CAP. They also diminished the potentiating effect of 5HT on ADP-induced platelet aggregation. It can be concluded that these effects may be a secondary mechanism of action in vivo. Thus “serotonergic component” of studied drugs should be taken under consideration at least in therapy of hypertension.Supported by CPBR, no 11.6

LACTIC DEHYDROGENASE OF THE MAMMALIAN ERYTHROCYTE: III. THE FORMATION OF A COMPLEX OF THE ENZYME WITH DPN AND LACTATE

1958 ◽  
Vol 36 (10) ◽  
pp. 1093-1098 ◽  
Author(s):  
Paul Ottolenghi ◽  
Orville F. Denstedt
Keyword(s):  
Ternary Complex ◽  
Kinetic Studies ◽  
Lactic Dehydrogenase ◽  
Binary Complex ◽  
Hydrogen Ions ◽  
Mammalian Erythrocyte

In the transfer of hydrogen ions and electrons from lactate to DPN by lactic dehydrogenase the lactate is capable of forming a complex only with the binary complex of enzyme and coenzyme to form an active ternary complex. The results of kinetic studies indicate that the site for the binding of lactate is on the DPN molecule itself.

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