ANALOGUES 



Pantothenic aldehyde was only slightly active as a growth stimulant 

 for L. helveticus, but had one-fifth the activity of pantothenic acid for 

 rats.^ 



Growth Inhibitors 



The preparation of pantoyltaurine ^i. 22, 30, 31 g^j^^j j^g inhibitory 

 action on the growth of micro-organisms have already been described 

 (page 381). Pantoyltaurine is perhaps the best known of the growth 

 inhibitors allied to pantothenic acid, from which it differs in the 

 replacement of the carboxyl by a sulphonic acid group. It is believed 

 to compete with pantothenic acid for an active enzyme system of which 

 pantothenic acid is the prosthetic group, presimiably coenzyme A, and 

 the two are able to displace one another from combination with the 

 enzyme. The ratio of the concentration of pantoyltaurine to that of 

 pantothenic acid necessary to inhibit bacterial growth, a ratio which 

 H. Mcllwain ^^ has termed the " antibacterial index ", varies from 500 

 for Streptococcus haemolyticus and exacting strains of Corynebacterium 

 diphtheriae to 1000 for Diplococcus pneumoniae and Lactobacillus 

 arabinosus, 5000 for non-exacting strains of C. diphtheriae, 8000 for 

 Streptococcus faecalis and Propionibacterium pentosaceum and 133,000 

 for Lactobacillus pentosus and Leuconostoc mesenteroides. Pantoyl- 

 tauramide was considerably less effective against these organisms, ^^ its 

 antibacterial index ranging from 2000 for S. haemolyticus and 2000 to 

 10,000 for the exacting strains of C. diphtheriae to 10,000 to 50,000 for 

 Diplococcus pneumoniae ; it failed to inhibit the other organisms tested. 

 The antibacterial index of homopantoyltaurine ^i (j3S-dihydroxy-yy- 

 dimethylvaleryltaurine) was 20,000 when tested on 5. haemolyticus.^^ 



The above data were obtained with the aid of racemic pantoyl- 

 taurine and pantoyltauramide. E. E. Snell ^^ tested the isomers 

 prepared from (-}-)- and (— )-pantolactone, and found that the sul- 

 phonic acid from the (—) -lactone was ten times as active as that from 

 the (-h) -lactone, in spite of the fact that partial racemisation had 

 undoubtedly occurred during the condensation. Thus growth inhibi- 

 tion showed the same configurational specificity as did growth promo- 

 tion by pantothenic acid. 



There appears to be a divergence of opinion concerning the ability 

 of pantoyltaurine to cause s3nnptoms of pantothenic acid deficiency in 

 animals. According to Snell et al}^ long-continued daily oral adminis- 

 tration at a dose level of 200 mg. per kg. of bodyweight produced such 

 symptoms in three to four weeks, but other workers failed to produce 

 symptoms of pantothenic acid deficiency in mice,^^ hamsters ^* and 

 rats.^^ 



Desoxypantoyltaurine (a-hydroxy-/S^-dimethylbutyryltaurine) un- 

 like pantoyltaurine, did not inhibit bacterial growth, nor did it 



397 



