280 PYRIDOXINE AND RELATED COMPOUNDS 



teracted by vitamin Be .^'^ The mechanism by which excess thiamine causes 

 a condition of vitamin Be deficiency in such organisms is not known. 



The retiuirement for vitamin Be in the synthesis of nicotinic acid, noted 

 in animals,!^^ becomes apparent in a widely used assay method for vitamin 

 Be which employs Saccharomyces carisbergensis 4228. This organism grows 

 very well in the absence of nicotinic acid when vitamin Be is present in 

 excess, and consequently nicotinic acid was not included in the initially 

 proposed assay medium J'^^ With suboptimal amounts of vitamin Be , how- 

 ever, nicotinic acid gives an "extra" growth response^"**^ • ^'^^ and must there- 

 fore be added to the medium when this is used for the determination of 

 vitamin Be in natural materials. 



D. IN MAN 

 P. GYORGY 



Vitamin Be is required in the nutrition of all species of animals studied. 

 Its role in metabolic processes is multiple and involves a large number of 

 biochemical reactions. Deficiency of vitamin Be in animals manifests itself 

 first in retardation of growth, which in itself is no indication for lack of a 

 specific essential nutrient. This is followed by a variety of more character- 

 istic manifestations of vitamin Be deficiency, such as cutaneous changes, 

 microcytic anemia, convulsions, etc. 



In general, it is expected that vitamins required by a large number of 

 vertebrates are also necessary dietary constituents for man. Thus, it ap- 

 peared to be reasonable to predict that there must be a human dietary 

 requirement for vitamin Be . However, in contrast to the great majority of 

 vitamins no pathological or clinical conditions in human beings were known 

 or identified up to the most recent past which could have been related to 

 deficiency of vitamin Be . As a matter of fact, the very widespread occur- 

 rence of vitamin Be in food products made it a priori improbable that a 

 major deficiency of vitamin Be could develop in man. In the absence of 

 such clear-cut deficiency conditions for vitamin Be there were three possi- 

 bilities open to investigate the need for vitamin Be by man: (1) through 

 the experimental production of vitamin Be deficiency; (2) through bio- 

 chemical procedures which should detect even the initial stage of vitamin 

 Be deficiency or a metabolic disarrangement indicating an increased re- 

 quirement for vitamin B e, and (3) through therapeutic tests in specific 

 clinical conditions. 



138 C. T. Ling, D. M. Hegsted, and F. J. Stare, /. Biol. Chem. 174, 803 (1948). 



139 L. Atkin, A. S. Schultz, W. L. Williams, and C. N. Frc}-, Ind. Eng. Chem. Anal. 

 Ed. 15, 141 (1943). 



'^» R. H. Hopkins and H. .1. Pennington, Biochem. J. 41, 110 (1947). 

 1" J. C. Rabinowitz n,iid I-]. E. Snell, J. Biol. Chem. 176, 1147 (1948). 



