Microassays for glucose 6-phosphate and 6-phosphogluconate based on bioluminescent techniques

Microassays for glucose 6-phosphate (G6P) and 6-phosphogluconate (6PG) capable of measurements in the picomole range are described. In these assays NADP+ reduction is coupled stoichiometrically to the oxidation of G6P or 6PG using glucose-6-phosphate dehydrogenase or 6-phosphogluconic dehydrogenase, respectively. The NADPH produced by these redox reactions is measured by bioluminescent technique using NADPH-specific bacterial luciferase. Problems encountered with these assays are detailed. To demonstrate the application of these methods for measurements in biological tissues, measurements of G6P and 6PG levels in mucosal cells from the turtle urinary bladder are presented.