The nature of the carbon dioxide substrate and equilibrium constant of the 6-phosphogluconate dehydrogenase reaction.

1. It was shown that dissolved CO(2) and not HCO(3) (-) or H(2)CO(3) is the primary substrate for reductive carboxylation with 6-phosphogluconate dehydrogenase from sheep liver. 2. The equilibrium constant of the reaction was measured in solutions of various ionic strengths and at several temperatures, and the free energy and heat of reaction were determined.