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G H CLOWES

Publications and source records attributed to G H CLOWES.

53 records · Page 3Linked to original sources
PubMed1955

Glucose-6-phosphate and 6-phosphogluconate dehydrogenases from eggs of the sea urchin, Arbacia punctulata.

1. Glucose-6-phosphate and 6-phosphogluconate dehydrogenases have been found in homogenates of Arbacia eggs; 95 per cent of the activity toward each substrate is recovered in the supernatant fraction after centrifuging at 20,000 g for 30 minutes. 2. With glucose-6-phosphate as substrate) the rate of TPN reduction by the supernatant fraction from 1 gm. wet weight unfertilized or fertilized eggs was 1.8 to 3.0 micromoles per minute; this rate is sufficient to support a rate of oxygen consumption 24 times that observed for unfertilized, and 6 times that for fertilized, eggs. Pentose was formed from glucose-6-phosphate at a rate 0.3 to 0.5 that of TPN reduction, when both rates were expressed as micromoles per minute. 3. The concentrations of glucose-6-phosphate and 6-phosphogluconate for half maximal activity were each approximately 0.00004 M for the respective enzymes in the supernatant fraction. Maximal activity toward 6-phosphogluconate was 50 to 60 per cent of that toward glucose-6-phosphate. Glucose-6-phosphate dehydrogenase activity was 50 per cent inhibited in presence of 0.00006 M 2,4,5-trichlorophenol. 4. Reduction of DPN by the supernatant fraction in presence of fructose-1,6-diphosphate and ADP was 0.1 to 0.2 micromoles per minute per gm. wet eggs, indicating that the glycolytic pathway can metabolize glucose-6-phosphate at about 5 per cent the rate at which it can be oxidized by the TPN system from unfertilized or fertilized Arbacia eggs. 5. Phosphoglucomutase, hexose isomerase, and a phosphatase for fructose-1,6-diphosphate also appear to be present in Arbacia eggs.

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PubMed1954

Hexokinase activity from eggs of the sea urchin Arbacia punctulata.

1. The hexokinase activity of homogenates of eggs and embryos of the sea urchin Arbacia punctulata has been measured. Expressed as micrograms glucose consumed at 20 degrees C., per hour per milligram of protein the following values were obtained: unfertilized eggs, 67; fertilized eggs, 72; 24 hour plutei, 94; 48 hour plutei, 226. The concentration of the enzyme in the eggs is small and may be calculated to be about 0.001 per cent of the dry weight of unfertilized eggs. 2. The hexokinase activity of the egg homogenate was virtually all recovered in the supernatant fraction when the homogenate was centrifuged at 20,000 x g for 30 minutes and was found to have the following properties: The concentrations for half maximal hexokinase activity with various substrates were, approximately: Glucose, 0,00003 M; fructose, 0.00075; mannose, 0.00007; 2-desoxyglucose, 0.00025. The relative rates of phosphorylation of various sugars by the supernate fraction when saturated with substrate were, approximately: Glucose, 1.0; mannose, 1.2; fructose, 1.8; 2-desoxyglucose, 2.0; glucosamine, 0.6. Adenosinediphosphate and glucose-6-phosphate inhibited the enzyme. No evidence for more than one hexokinase in the Arbacia extracts was found.

Animals↗