d-Lacticodéshydrogénase de la levure anaérobie etude de l'inactivation irréversible par un chélateur
1961; Elsevier BV; Volume: 50; Issue: 1 Linguagem: Inglês
10.1016/0006-3002(61)91058-7
ISSN1878-2434
AutoresE. Stachiewicz, Françoise Labeyrie, Andrée Curdel, Piotr P. Słonimski,
Tópico(s)Biochemical Acid Research Studies
ResumoThe kinetics of inactivation by Versene of d-lactate dehydrogenase from anaerobic yeast was studied. Inactivation is irreversible: a diminution of free Versene concentration down to 10−14M does not lead to any reactivation. The initial velocity of inactivation is proportional to Versene concentrations and to enzyme concentrations. The Michaelis constant (in the reaction d-lactate to pyruvate) of the partially inactivated enzyme is not modified. Activation energy of inactivation is low (⩽ 3kcal/mole). d-Lactate (but not l-) protects the enzyme from inactivation by decreasing the velocity of inactivation. Neither the acceptors nor flavine-adenine dinucleotide protect. Variation of initial inactivation velocity in relation to d-lactate concentration during the inactivation follows a hyperbolic kinetics: d-lactate concentration giving half protection is 7 · 10−6M, that is 300 times smaller than the Michaelis constant. Inactivation of d-lactate dehydrogenase by Versene is therefore due to the loss of a metal ion that is necessary for enzyme activity. A hypothesis is advanced that the fixation of the substrate takes place in the vicinity of the metal.
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