scholarly journals Pyruvate carboxylation in the rat heart. Role of biotin-dependent enzymes

1989 ◽  
Vol 257 (3) ◽  
pp. 913-916 ◽  
Author(s):  
K E Sundqvist ◽  
J K Hiltunen ◽  
I E Hassinen
Keyword(s):  
Heart Muscle ◽  
Malic Enzyme ◽  
Rat Heart ◽  
Pyruvate Carboxylase ◽  
Mass Action ◽  
Kinetic Properties ◽  
Biotin Deficiency ◽  
Perfused Rat Heart ◽  
Pyruvate Carboxylation

Pyruvate carboxylation in the isolated perfused rat heart was studied under steady-state conditions. A biotin deficiency resulting in a 90% decrease in myocardial pyruvate carboxylase left the pyruvate carboxylation rate unchanged. Pyruvate carboxylation in heart muscle must therefore take place by means of an enzyme which does not contain biotin. The kinetic properties and mass-action ratio of the NADP-linked malic enzyme in heart muscle can be taken as circumstantial evidence in favour of the role of malic enzyme in pyruvate carboxylation in myocardium.

scholarly journals Role of NADP+-linked malic enzymes as regulators of the pool size of tricarboxylic acid-cycle intermediates in the perfused rat heart

1987 ◽  
Vol 243 (3) ◽  
pp. 853-857 ◽  
Author(s):  
K E Sundqvist ◽  
J Heikkilä ◽  
I E Hassinen ◽  
J K Hiltunen
Keyword(s):  
Malic Enzyme ◽  
Rat Heart ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Mass Action ◽  
Acid Cycle ◽  
Perfused Rat Heart ◽  
Order Of Magnitude ◽  
Propionate Oxidation ◽  
Tricarboxylic Acid Cycle Intermediates

Cytosolic and mitochondrial concentrations of malate, 2-oxoglutarate, isocitrate and pyruvate in the isolated perfused rat heart were measured by non-aqueous tissue fractionation, taking the NADP-linked isocitrate dehydrogenase as indicator reactions for the free [NADPH]/[NADP+] ratios. The mass-action ratios of NADP-linked malic enzymes (EC 1.1.1.40) were found to be on the side of pyruvate carboxylation by more than one order of magnitude in both the cytosolic and the mitochondrial spaces in hearts perfused with glucose, whereas during propionate perfusion this ratio approached the equilibrium constant (Keq.) of malic enzyme. The results consequently indicate that the NADP-linked malic enzymes cannot be responsible for the feed-out (cataplerotic) reactions from the tricarboxylic acid cycle which occur during glucose perfusion. Only when other anaplerotic fluxes into the cycle are high, as during propionate oxidation, which results in accumulation of tricarboxylic acid-cycle intermediates, is a steady state reached which allows efflux via the malic enzyme.

Role of Endothelin During Reperfusion After Ischemia in Isolated Perfused Rat Heart

1994 ◽  
Vol 24 (6) ◽  
pp. 867-874 ◽  
Author(s):  
Patrick H. Dagassan ◽  
Volker Breu ◽  
Martine Clozel ◽  
Jean-Paul Clozel
Keyword(s):  
Rat Heart ◽  
Perfused Rat Heart ◽  
Isolated Perfused Rat Heart
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