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Biomedical subjects

M A Page

Publications and source records attributed to M A Page.

31 records · Page 2Linked to original sources
PubMed1978

Some properties of 3-hydroxy-3-methylglutaryl-coenzyme A synthase from ox liver.

Mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase (EC 4.1.3.5) was purified from ox liver, and obtained essentially free from 3-oxoacyl-CoA thiolases. The kinetic behaviour, like that of the synthases from chicken liver and yeast, is compatible with a reaction pathway involving condensation of an acetyl-enzyme with acetoacetyl-CoA. The Km for acetoacetyl-CoA, less than 1 micronM at pH 7.8, may possibly be low enough to permit rapid ketogenesis under physiological conditions without the need for a binary complex between the synthase and oxoacyl-CoA thiolase.

Acetyl Coenzyme A↗
PubMed1975

Glucose metabolites in blood and adipose tissue of obese diabetic and non-diabetic subjects.

1. Glucose 6-phosphate, fructose 6-phosphate, fructose diphosphate, glycerol phosphate and uridine diphosphate glucose have been measured in human adipose tissue and blood from obese subjects under fed and fasting conditions and in obese diabetic and non-diabetic subjects before and after an oral glucose load (100 g). 2. Adipose tissue metabolites expressed as nmol/g wet weight correlated inversely with adipocyte diameter. 3. After fasting, fructose diphosphate and glycerol phosphate in adipose tissue decreased significantly. 4. The basal concentrations of metabolites in blood and adipose tissue were maintained at similar concentrations in diabetic and non-diabetic subjects despite very different blood glucose concentrations. 5. The significant increase in adipose tissue glucose 6-phosphate after the glucose load seen in the non-diabetic but not in the diabetic subjects suggest that glucose uptake is decreased in the diabetic adipocyte.

Adipose Tissue↗
PubMed1971

Activities of enzymes involved in acetoacetate utilization in adult mammalian tissues.

1. The activities in rat tissues of 3-oxo acid CoA-transferase (the first enzyme involved in acetoacetate utilization) were found to be highest in kidney and heart. In submaxillary and adrenal glands the activities were about one-quarter of those in kidney and heart. In brain it was about one-tenth and was less in lung, spleen, skeletal muscle and epididymal fat. No activity was detectable in liver. 2. The activities of acetoacetyl-CoA thiolase were found roughly to parallel those of the transferase except for liver and adrenal glands. The high activity in the latter two tissues may be explained by additional roles of thiolase, namely, the production of acetyl-CoA from fatty acids. 3. The activities of the two enzymes in tissues of mouse, gerbil, golden hamster, guinea pig and sheep were similar to those of rat tissues. The notable exception was the low activity of the transferase and thiolase in sheep heart and brain. 4. The activities of the transferase in rat tissues did not change appreciably in starvation, alloxan-diabetes or on fat-feeding, where the rates of ketone-body utilization are increased. Thiolase activity increased in kidney and heart on fat-feeding. 5. The activity of 3-hydroxybutyrate dehydrogenase did not change in rat brain during starvation. 6. The factors controlling the rate of ketone-body utilization are discussed. It is concluded that the activities of the relevant enzymes in the adult rat do not control the variations in the rate of ketone-body utilization that occur in starvation or alloxan-diabetes. The controlling factor in these situations is the concentration of the ketone bodies in plasma and tissues.

Acetoacetates↗
PubMed1971

Activities of enzymes of ketone-body utilization in brain and other tissues of suckling rats.

1. The activities of 3-hydroxybutyrate dehydrogenase and 3-oxo acid CoA-transferase in rat brain at birth were found to be about two-thirds of those of adult rat brain, expressed per g wet wt. The activities rose throughout the suckling period and at the time of weaning reached values about three times higher than those for adult brain. Later they gradually declined. 2. At birth the activity of acetoacetyl-CoA thiolase in rat brain was about 60% higher than in the adult. During the suckling period there was no significant change in activity. 3. In rat kidney the activities of the three enzymes at birth were less than one-third of those at maturity. They gradually rose and after 5 weeks approached the adult value. Similar results were obtained with rat heart. 4. The activity of glutamate dehydrogenase (a mitochondrial enzyme like 3-hydroxybutyrate dehydrogenase and 3-oxo acid CoA-transferase) also rose in brain and kidney during the suckling period, but at no stage did it exceed the adult value. 5. Throughout the suckling period the total ketone-body concentration in the blood was about six times higher than in adult fed rats, and the concentration of free fatty acids in the blood was three to four times higher. 6. It is concluded that the rate of ketone-body utilization in brains of suckling rats is determined by both the greater amounts of the key enzymes in the tissue and the high concentrations of ketone bodies in the blood. In addition, the low activities of the relevant enzymes in kidney and heart of suckling rats may make available more ketone bodies for the brain.

Acyltransferases↗