Catalysis of pentose phosphate pathway reactions by cytoplasmic fractions from muscle, uterus and liver of the rat, and the presence of a reduced nicotinamide-adenine dinucleotide phosphate-triose phosphate oxidoreductase in rat muscle.
1. The enzymes of the pentose phosphate pathway were assayed in supernatant fractions from rat muscle, liver and uterus. 2. On incubation of ribose 5-phosphate with uterus and liver supernatants, triose phosphate, sedoheptulose 7-phosphate and hexose monophosphate accumulated. 3. When a muscle supernatant was used, glycerol 3-phosphate instead of triose phosphate appeared and there was a negligible accumulation of hexose monophosphate. 4. Hexose monophosphate production from ribose 5-phosphate was also followed by measuring NADP(+) reduction in the presence of an excess of phosphoglucose isomerase, glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase. 5. With a muscle supernatant, NADPH was reoxidized as rapidly as it was formed owing to the presence of a NADPH-triose phosphate oxidoreductase. 6. A modification of the pentose phosphate pathway in skeletal muscle incorporating this enzyme is proposed.
D000818:Animals; D002238:Carbohydrate Epimerases / Q000378:metabolism; D005260:Female; D005954:Glucosephosphate Dehydrogenase / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D008297:Male; D009132:Muscles / Q000201:enzymology / Q000378:metabolism*; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism*; D009928:Organ Specificity; D009943:Organophosphorus Compounds; D010428:Pentosephosphates / Q000378:metabolism*; D010734:Phosphogluconate Dehydrogenase / Q000378:metabolism; D051381:Rats; D012266:Ribose; D013056:Spectrophotometry, Ultraviolet; D014153:Transaldolase / Q000378:metabolism; D014174:Transketolase / Q000378:metabolism; D014306:Trioses; D014461:Ultracentrifugation; D014599:Uterus / Q000378:metabolism*
D009943:Organophosphorus Compounds; D010428:Pentosephosphates; D014306:Trioses; D012266:Ribose; D010734:Phosphogluconate Dehydrogenase; D005954:Glucosephosphate Dehydrogenase; D009247:NADH, NADPH Oxidoreductases; D014174:Transketolase; D014153:Transaldolase; D002238:Carbohydrate Epimerases