Purification and properties of glucose-6-phosphate dehydrogenase (NADP⁺/NAD⁺) and 6-phosphogluconate dehydrogenase (NADP⁺/NAD⁺) from methanol-grown Pseudomonas C

Glucose-6-phosphate dehydrogenase (d-glucose-6-phosphate:NADPH⁺ 1-oxidoreductase, EC 1.1.1.49) and 6-phosphogluconate dehydrogenase (6-phospho-d-gluconate:NADP⁺ 2-oxidoreductase, EC 1.1.1.43) have been purified from methanol-grown Pseudomonas C. Glucose-6-phosphate dehydrogenase exhibits activity with either NADP⁺ or NAD⁺ as coenzymes, V NADP⁺ = 0.96 V NAD⁺. K_m values of 22, 290, and 250 μM are obtained for NADP⁺, NAD⁺ and glucose -6phosphate (NADP⁺ as the coenzyme), respectively. ATP inhibits Glc-6P dehydrogenase activity with NAD⁺ as coenzyme and to a less extent the activity with NADP⁺. In the presence of MgCl₂, ATP inhibition of Glc-6P dehydrogenase activity is abolished. -. 6-Phosphogluconate dehydrogenase has a dual specificity for both NADP⁺ or NAD⁺ as coenzymes, V NADP⁺ = 1.66 V NAD⁺. K_m values of 20, 500 and 100 μM are obtained for NADP⁺, NAD⁺ and 6-phosphogluconate (NADP⁺ as the coenzyme), respectively. With NAD⁺ as the coenzyme ATP inhibits 6-phosphogluconate dehydrogenase activity, while with NADP⁺ as the coenzyme, activity was less affected. The possible role of these enzymes in the metabolism of one-carbon (C₁)-compounds in Pseudomonas C is discussed and compared with other methylotrphic microorganisms.