COMPETITIVE ANALOGUE-METABOLITE INHIBITION 467 



or oleic acid is required by Lactobacillus arabinosus for growth, it appears 

 that pantothenic acid functions in the conversion of acetate to oleic acid 

 or its equivalent. 12 



A strain of Leuconostoc mensenteroides which requires either acetate 

 or an aromatic amino acid (phenylalanine, tryptophan or tyrosine) for 

 growth is inhibited by N-pantoyl-n-butylamine. 5 The inhibition is pre- 

 vented competitively by pantothenic acid, resulting in an inhibition index 

 of 300 in the presence of either aromatic amino acids or acetate; but in 

 the presence of both an aromatic amino acid and acetate the inhibition 

 index is increased to 3,000. Phloroglucinol, particularly in the presence of 

 increased phosphate, was just as effective as the aromatic amino acids, 

 which are interchangeable in exerting this effect. Although ineffective 

 in replacing the aromatic compounds, sterols such as cholesterol and 

 coprosterone exert a sparing effect on the amount of phloroglucinol or 

 aromatic amino acids necessary to prevent the toxicity of the analogue 

 of pantothenic acid. The data suggest that pantothenic acid functions in 

 the biosynthesis of an intermediate common to the biosynthesis of all 

 these aromatic amino acids, and possibly to the biosynthesis of sterols 

 which are not readily reconverted to the intermediate. Phloroglucinol, 

 which can be considered a condensation product of three acetate radicals, 

 either is such an intermediate or is converted to it by the organism. 5 



In studies with Proteus morganii, the relative effects of glutamic acid 

 and cis- aconitic acid suggested that glutamic acid might be involved in 

 pantothenic acid metabolism in still an additional manner. Accordingly, 

 a number of synthetic conjugates of pantothenic acid, including those 

 with all the naturally occurring amino acids and with certain peptides, 

 have been prepared. 5 The conjugates containing glutamic acid were some- 

 what more active than pantothenic acid in preventing the toxicity of 

 analogues of pantothenic acid for certain lactic acid bacteria. 5 Concen- 

 trates of coenzyme A contain glutamic acid and glycine, 17 as well as 

 cysteine or cystine. 18 A naturally occurring conjugate of pantothenic 

 acid is also reported to contain glutamic acid. 19 



Biochemical Interrelationships Involving Biotin. The inhibitory effect 

 of y-(3,4-ureylenecyclohexyl) butyric acid on the growth of Lactobacillus 

 arabinosus is prevented competitively by biotin, resulting in an inhibition 

 index of approximately 30,000 in a medium from which aspartic acid is 

 omitted. 20 Either aspartic acid or oxalacetic acid affects the inhibition 

 in such a manner that the inhibition index is increased to approximately 

 300,000. Although sodium bicarbonate, particularly in the presence of 

 pyruvate, exerts an effect on the inhibition index, the two substances 

 together are not as effective as either aspartic acid or oxalacetic acid. 

 Oleic acid or "Tween 80" has no effect on the inhibitory action of the 



