Intramembraneous localization of rat liver microsomal hexose-6-phosphate dehydrogenase and membrane permeability to its substrates.

A method for purifying hexose-6-phosphate dehydrogenase (beta-D-glucose: NAD(P) -oxidoreductase, EC 1.1.1.47) from rat liver microsomes is described. The purified enzyme was shown to be homogeneous by sodium dodecyl sulfate (SDS)-polyacrylamide electrophoresis. It is shown that the enzyme is bound to the inner surface of microsomal membranes, and that glucose 6-phosphate, but not NADP, penetrates almost freely into the membranes at 37 degrees C.