576 



BIOTIN 



metabolic functions. The first suggestion regarding the enzymatic action 

 of biotin related it to the synthesis of aspartic acid^^'^^ and to the oxidation 

 of pyruvic acid,^^ the latter being probably the result of faulty carbon di- 

 oxide transfer in the absence of biotin.^* As further major functions the 

 deamination of certain amino acids and the biosynthesis of oleic acid, and 

 as minor functions the relationships to carbohydrate synthesis, succinic 

 acid dehydrogenase, and amino acid oxidase, should be mentioned. 



1. Biotin in Aspartic Acid Synthesis 



The sparing effect of aspartic acid on the biotin requirement of yeast 

 and the growth promotion of yeast by aspartic acid in partial replacement 

 of biotin"'^'^ has been extended to various species of bacteria. ^^"-*' 



The cellular synthesis of aspartic acid may involve three possible reac- 

 tions: (1) transamination, (2) the condensation of pyruvate and carbon 

 dioxide to yield oxalacetate (Wood-Werkman reaction-^), and (3) the direct 

 amination of fumaric acid, as illustrated by the following scheme. 



The fact that resting cells of Lactobacillus arabinosus, Streptococcus fae- 

 calis R., and L. casei are able to form aspartic acid from glutamic acid, 

 alanine, or cysteic acid plus oxalacetic acid at the same rate with or with- 



" D. Burk, R. J. Winzler, and V. du Vigneaud, Proc. Am. Soc. Biol. Chem., J . Biol. 

 Chem. 140, XXI (1941). 



12 S. A. Koser, M. H. Wright, and A. Dorfman, Proc. Soc. Exptl. Biol. Med. 51, 204 

 (1942). 



13 R. J. Winzler, D. Burk, and V. du Vigneaud, Arch. Biochem. 5, 25 (1944). 



»* F. J. Pilgrim, A. E. Axelrod, and C. A. Elvehjem, J. Biol. Chem. 145, 237 (1942). 



15 D. Burk and R. J. Winzler, Science 97, 57 (1943). 



»• J. L. Stokes, A. Larsen, and M. Gunness, J. Biol. Chem. 167, 613 (1947). 



" J. L. Stokes, A. Larsen, and M. Gunness, /. Bacteriol. 54, 219 (1947). 



" H. A. Lardy, R. L. Potter, and C. A. Elvehjem, /. Biol. Chem. 169, 451 (1947). 



>« W. Shive and L. J. Rogers, ./. Biol. Chem. 169, 453 (1947). 



" R. L, Potter and C. A. Elvehjem, J. Biol. Chem. 172, 531 (1948). 



2> C. n. Werkm;ui and 11. C. Wood, Botan. Rev. 8, 1 (1942). 



