Role of glycerol 3-phosphate dehydrogenase in glyceride metabolism. Effect of diet on enzyme activities in chicken liver.
1. The metabolic role of hepatic NAD-linked glycerol 3-phosphate dehydrogenase (EC 1.1.1.8) was investigated vis-a-vis glyceride synthesis, glyceride degradation and the maintainence of the NAD redox state. 2. Five-week-old chickens were placed on five dietary regimes: a control group, a group on an increased-carbohydrate-lowered-fat diet, a group on a high-fat-lowered-carbohydrate diet, a starved group and a starved-refed group. In each group the specific activity (mumol/min per g wet wt. of tissue) of hepatic glycerol 3-phosphate dehydrogenase was compared with the activities of the beta-oxoacyl-(acyl-carrier protein) reductase component of fatty acid synthetase, glycerol kinase (EC 2.7.1.30) and lactate dehydrogenase (EC 1.1.1.27). 3. During starvation, the activities of glycerol 3-phosphate dehydrogenase, glycerol kinase and lactate dehydrogenase rose significantly. After re-feeding these activities returned to near normal. All three activities rose slightly on the high-fat diet. Lactate dehydrogenase activity rose slightly, whereas those of the other two enzymes fell slightly on the increased-carbohydrate-lowered-fat diet. 4. The activity of the beta-oxoacyl-(acyl-carrier protein) reductase component of fatty acid synthetase, a lipid-synthesizing enzyme, contrasted strikingly with the other three enzyme activities. Its activity was slightly elevated on the increased-carbohydrate diet and significantly diminished on the high-fat diet and during starvation. 5. The changes in activity of the chicken liver isoenzyme of glycerol 3-phosphate dehydrogenase in response to dietary stresses suggest that the enzyme has an important metabolic role other than or in addition to glyceride biosynthesis.
D000818:Animals; D002645:Chickens; D004040:Dietary Carbohydrates / Q000378:metabolism*; D064429:Fatty Acid Synthases / Q000032:analysis; D005989:Glycerides / Q000378:metabolism*; D005991:Glycerol Kinase / Q000032:analysis; D005993:Glycerolphosphate Dehydrogenase / Q000378:metabolism*; D007770:L-Lactate Dehydrogenase / Q000032:analysis; D008099:Liver / Q000201:enzymology* / Q000378:metabolism; D009243:NAD; D013217:Starvation
D004040:Dietary Carbohydrates; D005989:Glycerides; D009243:NAD; D005993:Glycerolphosphate Dehydrogenase; D007770:L-Lactate Dehydrogenase; D064429:Fatty Acid Synthases; D005991:Glycerol Kinase