Kinetics of human erythrocyte hexokinase. Influence of temperature, ATP4− and magnesium ions
1976; Elsevier BV; Volume: 452; Issue: 2 Linguagem: Inglês
10.1016/0005-2744(76)90187-x
ISSN1878-1454
Autores Tópico(s)Neonatal Health and Biochemistry
ResumoHuman erythrocyte hexokinase (EC 2.7.1.1) is inhibited competitively with respect to Mg · ATP2− by uncomplexed Mg2+ (Ki = 16–18 mM) and ATP4− (Ki = 1.6 mM). No real activation by low concentrations of Mg2+ could be detected and no allosteric behaviour was observed under the conditions tested. The temperature dependence of the enzyme was studied in relationship to the presence of Mg2+ or ATP4−. At equal concentrations of Mg2+ and ATP4− a break in the Arrhenius plot was observed at 27.5°C, the higher temperature form of the enzyme having the lower activation energy. This break point in the Arrhenius plot was shifted to 36°C in the presence of 5 mM Mg2+. A straight-line relationship was observed in the presence of 2.5 mM ATP4−. The Km for Mg · ATP2− showed a linear increase at temperatures over about 36°C independent of the presence of Mg2+ or ATP4−. The nature of these phenomena is discussed.
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