Hexose-6-phosphate dehydrogenase: Distribution in rat tissues and effect of diet, age and steroids

Hexose-6-P dehydrogenase is a microsomal enzyme which oxidizes glucose-6-P, galactose-6-P, 2-deoxy-glucose-6-P, and glucose using either NAD or NADP as hydrogen acceptor. Its distribution was studied in rat tissues; the enzyme was found in liver, adrenals, spleen, kidney, heart, lungs, gluteal muscle, testes, ovaries, seminal vesicles, prostate, uterus, and intestine. No enzyme was detected in the brain and mammary gland. Hexose-6-P dehydrogenase is not inhibited by various steroids which are known to inhibit glucose-6-P dehydrogenase. Also, feeding of a diet containing 68% galactose, glucose, or fructose does not alter the activity of hexose-6-P dehydrogenase in rat liver. Liver hexose-6-P dehydrogenase activity increased rapidly before birth, and then declined gradually to adult levels. It appears possible the hexose-6-P dehydrogenase serves as a source of reduced pyridine nucleotides for mixed-function oxidase systems, but definitive evidence for its role in metabolism is lacking.