234 



PHYSIOLOGY OF THE FUNGI 



HO— CH2— C(CH3)2- 

 HO— CH2— C(CH3)2- 



CHOH— CO— NH- 



Pantothenic acid 



-CHOH— CO— NH- 



Pantoyltaurine 



CH2— CHo— COOH 



-CH2— CH2— SO3H 



Pantoyltaurine is the sulfonic-acid analogue of pantothenic acid. 

 Snell (1941) studied the competitive inhibition of yeast growth by pan- 

 toyltaurine and found that this compound was effective when pantothenic 

 acid was the metabolite supplied in the medium but that pantoyltaurine 

 did not compete with /3-alanine. The data in Table 40 illustrate this 

 difference. 



Table 40. The Effect of Pantoyltaurine on the Growth of Saccharomyces 

 cerevisiae in the Presence of Pantothenic Acid and (3-Alanine 

 Inoculum used, 0.02 mg., time of incubation, 16 hr. (Snell, Jour. Biol. Chem. 141, 

 1941.) 



The synthesis of pantothenic acid via /3-alanine by Escherichia colt 

 is inhibited by cysteic acid (sulfonic-acid analogue of aspartic acid). 

 This inhibition is reversed by /3-alanine or pantothenic acid (Ravel and 

 Shive, 1946). For further information concerning other pantothenic 

 acid and other antagonists, the review of Roblin (1946) should be 

 consulted. 



Pyridoxine antagonists. Some of the pyridoxine analogues studied 

 by Robbins and Ma (1942) inhibited the growth of Ceratostomella ulmi. 

 This inhibition was reversed by additional pyridoxine. The substitution 

 of an ethyl group for the methyl group of pyridoxine produced an antag- 

 onist for C. ulmi, but ethyl pyridoxine was as active for excised tomato 

 roots as pyridoxine itself. The above authors suggest that ethyl pyri- 

 doxine might be a chemotherapeutic agent for the Dutch elm disease. 

 The formulas of ethyl pyridoxine and desoxypyridoxine are given below : 



HO- 



C2H2- 



/^-CHoOH 



-CH2OH 



HO- 



/%— CH2OH 



\n^ 



CH3— 



Ethyl pyridoxine 



Desoxypyridoxine 



