578 



BIOTIN 



This indicates that inhibition of the growth effect of biotin interferes with 

 the biosynthesis of a-ketoglutaric acid, formed under usual circumstances 

 by decarboxylation of oxalosuccinic acid.^^ 



In a similar example of "inhibition analysis"^'-* in L. arahinosus, the anti- 

 bacterial index for competitive inhibition of biotin by 7-(3,4-ureylenecy- 

 clohexyl) butyric acid was increased tenfold by the addition of aspartic 

 acid or oxalacetic acid. Here apparently biotin regulates the synthesis of 

 oxalacetic acid. 



It has been further shown-^ that E. coli harvested from a complex me- 

 dium, on standing in molar phosphate at pH 4, rapidly lost the ability to 

 produce carbon dioxide from aspartic acid as well as from malic acid or 



" Adapted from Ochoa et al.^^ by Liclitetein.^s 

 Figures in parentlieses equal number of livers pooled in each case. 



oxalacetic acid. Addition of biotin restored this lost enzymatic function. 

 Although the metabolic product derived from malate in E. coli appears 

 to be different from oxalacetate, and there is no proof that under similar 

 conditions aspartic acid would be converted by E. coli to oxalacetic acid,-^ 

 the fact that E. coli rec^uires biotin to produce carbon dioxide from these 

 compounds indicates its functional role in decarboxylation. 



The decarboxylation of oxalacetate or the ability of malate to reduce 

 triphosphopyridine nucleotide has been found to be reduced in the livers 

 obtained from biotin-deficient turkeys.-^ Several other dehydrogenases 

 tested were not altered, and the effect of biotin appeared to be specific 

 (Table VIII). However, biotin restored the normal enzyme content only 



2^ S. Ochoa, A. Mehler, M. S. Blancharcl, T. H. Jukes, C. E. Hoffmann, and M. Regan, 



J. Biol. Chem. 170, 413 (1947). 

 *' H. C. Lichtstein, Vitamins and Hormones 9, 27 (1951). 



