Glucose-6-phosphate dehydrogenase from the hyperthermophilic bacterium Thermotoga maritima: Expression of the g6pd gene and characterization of an extremely thermophilic enzyme

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Abstract

The gene (open reading frame Tm1155, g6pd) encoding glucose-6-phosphate dehydrogenase (G6PD, EC 1.1.1.49) of the hyperthermophilic bacterium Thermotoga maritima was cloned and functionally expressed in Escherichia coli. The purified recombinant enzyme is a homodimer with an apparent molecular mass of 95 kDa composed of 60-kDa subunits. Rate dependence (at 80°C) on glucose-6-phosphate and NADP+ followed Michaelis-Menten kinetics with apparent Km values of 0.15 mM and 0.03 mM, respectively; apparent Vmax values were about 20 U mg-1. The enzyme also reduced NAD+ (apparent Km 12 mM, Vmax 12 U mg-1). The 1000-fold higher catalytic activity (kcat/Km) with NADP+ over NAD+ defines the G6PD as NADP+ specific in vivo. G6PD activity was competitively inhibited by NADPH with a Ki value of 0.11 mM. With a temperature optimum of 92°C the enzyme is the most thermoactive G6PD described. © 2002 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.

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Hansen, T., Schlichting, B., & Schönheit, P. (2002). Glucose-6-phosphate dehydrogenase from the hyperthermophilic bacterium Thermotoga maritima: Expression of the g6pd gene and characterization of an extremely thermophilic enzyme. FEMS Microbiology Letters, 216(2), 249–253. https://doi.org/10.1016/S0378-1097(02)01021-2

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