1. Under the present conditions of experiment, Arbacia eggs were found to contain an average of 110 mg. of acid-hydrolyzable carbohydrate (calculated as glucose) per gm. of egg protein. This carbohydrate was almost all in the egg proper, little or none being found in the jelly. To permit conversion of the data to other bases of reference the relation of nitrogen content to wet and dry weight and to egg number were determined. The eggs were found to contain 23.9 per cent solids, 0.10 mg. nitrogen per mg. dry weight, and 5.93 mg. nitrogen per 106 cells. From these results, about 7 per cent of the egg dry weight is acid-hydrolyzable carbohydrate and about 65 per cent is protein. 2. Approximately one-half of the total acid-hydrolyzable carbohydrate was isolated in the form of an alkali-stable, alcohol-precipitable carbohydrate. This substance gave a typical glycogen color test with iodine, yielded glucose on acid hydrolysis, and had, within the limits of experimental error, the same optical rotation as glycogen from other animal sources. Since known amounts of glycogen were completely recovered when carried through the isolation process, the nature of one-half of the acid-hydrolyzable carbohydrate of Arbacia eggs remains undetermined. 3. In order to gain some estimate of the extent to which Arbacia eggs utilize their total carbohydrate for development, determinations of the oxygen consumption, respiratory quotient, carbohydrate consumption, lactic acid production, and ammonia production were made. While all samples of eggs were found to utilize carbohydrate from the 15th to the 24th hours of development at 20°C., certain samples of eggs consumed little or no carbohydrate from the 1st to the 6th hours, the period during which cell division proceeds most rapidly. In a number of instances where carbohydrate breakdown was lacking, a substantial proportion of the oxygen consumption could be accounted for on the basis of processes involving oxidation of protein or protein breakdown products.
Glucose-6-phosphate dehydrogenase (Zwischerfferment) and 6-phosphogluconate dehydrogenase, first studied in y e a s t by Warburg and his coworkers (1, 2), have since been found in a number of cells and tissues. These have received extensive study because they provide a pathway for formation of pentose phosphate from hexose phosphate and because of the possibility that oxidation of glucose-6-phosphate by this means may provide energy for function. (See references 3--6.)The present experiments deal with the occurrence, the properties, and the relation to over-all metabolism of these two enzymes in eggs of the sea urchin, Arbacia punctulata; they are part of a general survey of the enzymes of Arbacia eggs (7). Experimental MethodsThe eggs were obtained and handled as previously described (8, 9). Homogenates were prepared as before (9), except that citrate was omitted from, and 0.004 ~ ethylenediamine tetraacetic acid included in, the homogenizing medium to minimize breakdown of the echinochrome granules; the homogenates were a light orange-pink and the supernatant fractions obtained therefrom by centrifugation at 20,000 g for 30 minutes were clear and of a straw yellow color. The homogenates and other fractions to be tested were kept at ice water temperature; full activity was retained for 6 to 8 hours; 20 to 40 per cent of the initial activity of the homogenate or supematant fractions was lost by a single freezing and thawing; this procedure appeared relatively more damaging to the phosphogluconate dehydrogenase than to glucose-6-phosphate dehydrogenase. The values recorded in the tables and figures were calculated by use of the conversion factors previously derived (10).The sources of the special reagents were: Sigma Chemical Company, triphosphopyridine nucleotide (TPN), 83 per cent purity (assayed by yeast Zwischenferment), barium glucose-l-phosphate, and yeast Zwischenferment (lot No. 54-137, virtually free of phosphogluconate dehydrogenase);
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