D. E. GREEN 



systems. But the success in the field of glycolysis has been to some 

 extent at the expense of progress in other fields. 



Nutrition in essence deals with the relative amounts and nature 

 of the materials which have to be supplied ultimately to the enzyme 

 systems, and with the resyntheses and replacement of enzymes. In 

 other words, the study of nutrition and the study of enzymes represent 

 two sides of the same coin. Since the nature, number, and amounts of 

 enzymes vary from one living system to another, the nutritional problem 

 varies in the same way. If we knew all the enzymes present in a par- 

 ticular organism and the special components present in each of the 

 enzymes, theoretically, we would have all the necessary data for 

 determining the complete nutritional requirements. But since we are 

 largely in the dark about the vast majority of enzymes, we use the data 

 and knowledge of nutrition to ferret out information about enzymes. 

 It has long been known, for example, that traces of certain metals 

 such as manganese, iron, zinc, copper, and magnesium are essential 

 in the diets of many animals. The indispensability of these metals 

 in the diet has been correlated with the presence of these metals as 

 structural elements of important enzyme systems. Thus, manganese 

 has been shown to be an essential component of arginase; magnesium 

 an essential component of carboxylase, chlorophyll, etc.; zinc of car- 

 bonic anhydrase; copper of phenolases; and iron of catalase, per- 

 oxidase, cytochromes, and lactic dehydrogenase. Traces of cobalt 

 are known to be essential in the diets of sheep particularly. No doubt 

 cobalt also will be identified as an essential component of some as yet 

 unknown system. Among plants, boron and molybdenum are es- 

 sential trace elements, and one must presume special enzyme systems 

 in plants requiring these elements. The fact that, in most instances, 

 small quantities of the metals are necessary correlates with the extraor- 

 dinary activity of enzymes at high dilutions. In other words, only 

 traces of metals are necessary for incorporation into the enzymes, since 

 the enzymes also occur only in trace amounts. 



The identification of the P-P factor with nicotinamide, of vita- 

 min Bi with thiamin, of vitamin B2 with riboflavin, and of vitamin 

 Be with pyridoxal provides a moral for those who prefer to study one 

 side of a coin without reference to the other. Cozymase, a dinucleotide 

 of nicotinamide and adenine, has long been studied as the coenzyme 

 of fermentation since its discovery by Harden and Young (4) in 1906. 



