The pyridine nucleotide-dependent D-glucose dehydrogenase of Nostoc sp. strain Mac, a cyanobacterium, is subject to thioredoxin modulation

Abstract

AbstractA pyridine nucleotide-dependent D-glucose dehydrogenase (GDH) was isolated and purified about 1000-fold from Nostoc sp. strain Mac. The activity of this preparation with NADP as cofactor was 2.8-times that with NAD. This ratio did not change during purification. The enzyme both in crude extracts and after purification proved to be subject to redox modulation. Homologous and heterologous (Anacystics nidulans, Anabaena sp. strain PCC 7120, spinach) thioredoxins, in the presence of 0.5 mM DTT, deactivated the enzyme. The thioredoxin from Nostoc was active with heterologous enzymes: it activated the fructose-1,6-bisphosphatase of Anacystis nidulans and the NADP-dependent malate dehydrogenase of spinach. The thioredoxin-mediated reduction decreased the apparent Vmax value for D-glucose by about 65% and that for NADP by about 51%. The apparent Km value for NADP increased upon reduction by about 10-fold. The apparent Km value for D-glucose was but slightly affected by the redox state of the enzyme