RESUMO
Glucose 6-phosphate dehydrogenase (G6PD) (EC 1.1.1.363) is a crucial regulatory enzyme in the oxidative pentose phosphate pathway that provides reductive potential in the form of NADPH, as well as carbon skeletons for the synthesis of macromolecules. In this study, we report the cloning, expression, and characterization of G6PD (SpG6PD1) from a lichen-associated psychrophilic bacterium Sphingomonas sp. PAMC 26621. SpG6PD1 was expressed in Escherichia coli as a soluble protein, having optimum activity at pH 7.5â»8.5 and 30 °C for NADP⺠and 20 °C for NADâº. SpG6PD1 utilized both NADP⺠and NADâº, with the preferential utilization of NADPâº. A high Km value for glucose 6-phosphate and low activation enthalpy (ΔH) compared with the values of mesophilic counterparts indicate the psychrophilic nature of SpG6PD1. Despite the secondary structure of SpG6PD1 being maintained between 4â»40 °C, its activity and tertiary structure were better preserved between 4â»20 °C. The results of this study indicate that the SpG6PD1 that has a flexible structure is most suited to a psychrophilic bacterium that is adapted to a permanently cold habitat.