Location and properties of glucose dehydrogenase in sporulating cells and spores of Bacillus subtilis

Abstract

Late during sporulation, B. subtilis produces glucose dehydrogenase (GlcDH; EC 1.1.1.47), which can react with D-glucose or 2-deoxy-D-glucose and can use nicotinamide adenine dinucleotide (NAD) or nicotinamide adenine dinucleotide phosphate (NADP) as a cofactor. This enzyme is found mainly in the forespore compartment and is present in spores; it is probably made exclusively in the forespore. The properties of GlcDH were determined both in crude cell extracts and after purification. The enzyme is stable at pH 6.5 but labile at pH 8 or higher; the pH optimum of enzyme activity is 8. After inactivation at pH 8, the activity can be recovered in crude extracts, but not in solutions of the purified enzyme, by incubation with 3 M KCl and 5 mM NAD or NADP. As determined by gel filtration, enzymatically active GlcDH has a molecular weight of about 115,000 (if the enzyme is assumed to be globular). GlcDH is distinct from a catabolite-repressible inositol dehydrogenase (EC 1.1.1.18), which can also react with D-glucose, requires specifically NAD as a cofactor, and has an electrophoretic mobility different from that of GlcDH.