624 THE BIOCHEMISTRY OF B VITAMINS 



mg). When larger amounts were administered, the urinary excretion of 

 pantothenic acid was decidedly greater after administration of panto- 

 thenyl alcohol than after administration of an equivalent amount of 

 either sodium or calcium pantothenate. 17, 27, 28 Pantothenyl alcohol can- 

 not replace pantothenic acid in the nutrition of lactic acid bacteria. On 

 the contrary, it inhibits the utilization of pantothenic acid by these 

 organisms, 19 as subsequently discussed. 



While /^-alanine but not pantoic acid can replace pantothenic acid in 

 the nutrition of some organisms such as yeast 29, 30 and some strains of 

 Corynebacterium diphtheriae, 3U3S pantoic acid, but not /^-alanine, is 

 effective in replacing the vitamin for other organisms such as Acetobacter 

 subdoxydans 621, 34 Streptococcus hemolyticus H 69 D, 35 and one strain of 

 Clostridium septicum 36 Either pantoic acid or /^-alanine alone accelerates 

 the rate of growth of certain strains of Brucella suis ; 37 the two combined 

 are more effective, but still are not as effective as the intact vitamin. 

 When capable of replacing pantothenic acid, pantoic acid usually is con- 

 siderably more active than pantolactone. 38 The results suggest that 

 pantolactone must be hydrolyzed before utilization in the synthesis of 

 pantothenic acid. 



Coenzyme A, 39 the coenzyme which accounts for the major portion of 

 the bound pantothenic acid, is inactive in replacing pantothenic acid in 

 the nutrition of numerous organisms. These include Lactobacillus ara- 

 binosus 17-5, Saccharomyces cerevisiae, and Lactobacillus casei. However, 

 coenzyme A administered intraperitoneal^ is fully active in the chick 

 assay, but on oral administration only 61 per cent of the activity was 

 observed. 40 Both coenzyme A 41 and a naturally occurring conjugate of 

 pantothenic acid 42 are appreciably more effective than pantothenic acid 

 in promoting the growth of Acetobacter suboxydans 621. A product ob- 

 tained from coenzyme A by enzymatic action of liver extracts has growth- 

 promoting properties for Acetobacter suboxydans similar to that of the 

 conjugate of pantothenic acid. 41 Intestinal phosphatase acts on coenzyme 

 A to form a still different product, which does not have enhanced ac- 

 tivity for Acetobacter suboxydans 41 and is not effective for other micro- 

 organisms. 43 Both intestinal phosphatase and liver enzymes are required 

 for the conversion of coenzyme A to a form which is utilized by Lacto- 

 bacillus arabinosus and most other microorganisms, and is presumably 

 free pantothenic acid. 43 



Inhibitory Analogues of Pantothenic Acid 



Pantoyltaurine. The first growth inhibition specifically and competi- 

 tively reversed by pantothenic acid was reported by Snell, 44 who pre- 

 pared and tested N-(cc,y-dihydroxy-/?,/?-dimethylbutyryl) taurine as an 



