knowledge of the metabolism of carbohydrates in aquatic animals is more 

 developed than is our knowledge for the other biochemical entities of 

 great importance in metabolism. It seems desirable to summarize present 

 knowledge in the form of diagrams of metabolic pathways, which have found 

 popular use xn textbooks of biochemistry such as Outlines of Enzyme Chem- 



istryjNieland and Stumpf 1955) and Dynamic Aspect's of Biochemistry 



(.Baldwin 1952). From these and other sources Ihe reader can see the de- 

 tailed information that is available on land animals, plants, and bacteria. 

 In figure 1 is summarized the known intermediary metabolism of carbohy- 

 drates in teleosts and elasraobranchs. Considering the importance of 

 carbohydrate metabolism in supplying energy from carbohydrate foods, it 

 can be seen that our knowledge is very fragmentary. There is no real in- 

 formation on the many metabolic transformations in glycolysis except for 

 that on the formation of pyruvate from phosphopyruvate by pyruvate phos- 

 phof erase. Evidence on the occurrence of the hexosemonophosphate shunt 

 is completely lacking. The known intermediary metabolism of carbohydrates 

 in aquatic mammals is shown in figure 2. The identification of five of 

 the important Embden-Meyerhof intermediates suggests that this pathway 

 of metabolism is operative in aquatic mammals, but much more detailed in- 

 formation is needed for confirmation. There is no information on the hex- 

 osemonophosphate shunt. The known intermediary metabolism of carbohydrates 

 in oysters is shown in figure 3» Here also, the positive identification 

 of seven important intermediates suggests that the Embden-Meyerhof pathway 

 of glycolysis is operative in the oyster. Much more detailed information, 

 especially identification of the enzymes catalyzing the transformations 

 in glycolysis, is needed. Again, there is no evidence of the hexose- 

 monophosphate shunt. The known intermediary metabolism of carbohydrates 

 in the sea urchin is shown in figure ii. The identification of five im- 

 portant enzymes catalyzing reactions in the Embden-Meyerhof pathway suggests 

 that this pathway is operative in the sea urchin. Even though the sea 

 urchin has been an aquatic animal of choice for many biochemical studies, 

 our evidence for the existence of this important metabolic pathway is far 

 from complete. It would be very desirable to have positive identification 

 of the occurrence of the intermediates of glycolysis in the sea urchin. 

 The identification of two enzymes of the hexosemonophosphate shunt suggests 

 that this shunt is operative in the sea urchin, but much more information 

 is needed for a definite conclusion. 



TRICARBOXYLIC ACID OTCLE AND TERMINAL OXIDATION 



The process of glycolysis, which apparently functions in marine 

 animals, usually results in the formation of pyruvate, which is com- 

 pletely oxidized by the series of enzymatic reactions comprising the tri- 

 carboxylic acid cycle. In animals, plants, and bacteria that have been 

 more extensively studied, the acetyl coenzyme A, formed by oxidative 

 decarboxylation of pyruvate, enters the TCA cycle by reacting with oxa- 

 lacetatej and upon completion of one cycle, three molecules of carbon 

 dioxide are produced with the regeneration of oxalacetate. Since the 

 TCA cycle establishes a link between the metabolism of carbohydrate^ 

 and that of lipids and protein and thereby provides a means for their 

 interconversion and complete oxidation for production of energy, it is 

 important that we have knowledge of this metabolic cycle in marine ani- 

 mals. 



8 



