is that found in other tissues of this animal, the sperm probably depends 

 upon oxidative metabolism almost completely. The respiration of homogen- 

 ates of oyster eggs is stimulated by some of the intermediates of glycoly- 

 sis, such as glycogen, fructose, glucose, glycerol, and glycerophosphate 

 (Cleland 1950). 



Rather extensive investigation of the metabolism of the eggs of 

 Arbacia punctulata and other sea urchins has been carried out over a 

 number of years. The emphasis of these studies is on the chemical events 

 taking place with fertilization and the processes by which energy is 

 liberated for cleavage and development. A review of this information 

 covering the period from 1932 to 19h9 has been presented by Krahl (1950) 

 and is mainly concerned with the nature and interrelationships of the 

 catalysts by which the Arbacia egg derives energy from foodstuffs. At 

 that time, none of the enzymes of glycolysis had been studied in this 

 species. The carbohydrate and glycogen content was known (Hutchens et al. 

 19U2); however, oxidation of glucose, lactate, 2-glycerophosphate, succi- 

 nate, or butyrate could not be demonstrated with cytolysates of Arbacia eggs 

 (Ballentine 19 U0). 



The observations of Cleland and Rothschild (195>2) from their study 

 of carbohydrate oxidation of the eggs of the sea urchin, Echinus esculentus , 

 were consistent with the assumption that the glycolytic pathway is oper- 

 ative in these animals. Oxygen uptake and lactic acid production of homo- 

 genized eggs were increased by adding glycogen, glucose, and fructose and 

 were stimulated by addition of diphosphopyridine nucleotide (DPN). The 

 phosphorylated intermediates of glycolysis such as glucose-1-phosphate, 

 fructose-6-phosphate, and fructose-l,6-diphosphate also stimulate the up- 

 take of oxygen. Pyruvate and lactate were shown to accumulate in homogen- 

 ized eggs under anaerobic conditions and in the presence of hydrogen cya- 

 nide. Other evidence presented by Cleland and Rothschild for glycolysis 

 includes inhibition of oxygen uptake by fluoride ion and its reversal by 

 pyruvate, and the accumulation of pyruvate after addition of glucose-6- 

 phosphate or hexose-diphosphate. teas (1950) reported the existence of 

 phosphoglucomutase, enolphosphopyruvic acid, phosphodihydroxyacetone, 

 enolase, aldolase, and oxoisomerase in eggs of sea urchins. 



Krahl et al. (195U a,b) have reported the occurrence of hexokinase, 

 phosphofructokinase, and aldolase in the supernatant and homogenates 

 of Arbacia eggs. Evidence that the hexosemonophosphate shunt also is 

 operative was' shown by the fact that triphosphopyridine nucleotide ( TPN) 

 was reduced and pentose was formed from glucose-6-phosphate and 6-phos- 

 phogluconate by these egg preparations. Indications are that glucose-6- 

 phosphate can be metabolized by the glycolytic pathway at only about 

 5 percent of the rate it can be oxidized by the TPN system. Krahl et al. 

 suggest that the latter system is probably the major pathway for utiliza- 

 tion of carbohydrate in Arbacia eggs. Other glycolytic enzymes present 

 in Arbacia eggs, as shown by TP'N reduction of the corresponding substrates, 

 are glucose-1-phosphate, phosphoglucomutase; fructose-6-phosphate, hex- 

 ose isomerasej and fructose-l,6-diphosphate, a fructose-l,6-diphosphatase 



