THE NICOTINIC ACID GROUP 611 



The order of activity reported is such that contamination with the vita- 

 min cannot be ruled out, particularly since other reports indicate 

 inactivity. 



Inhibitory Analogues of the Nicotinic Acid Group 



Although a large number of analogues of nicotinic acid and related 

 compounds have been tested as inhibitors, only a few have been reported 

 to inhibit competitively the functioning of nicotinic acid in biological 

 systems. 



3-Pyridinesulfonamide. The first specific reversal of the toxicity of 

 an analogue by nicotinamide was reported by Mcllwain, 04 who found 

 that the inhibition of growth of Staphylococcus aureus caused by 3- 



O 



-S0 2 NH 2 



3-pyridinesulfonamide 



pyridinesulfonamide was competitively prevented by the vitamin. The 

 inhibition indices were 50,000, 250,000 and 1,250,000 for incubation 

 periods of 19, 26 and 43-96 hours, respectively. Growth promoted by 

 nicotinic acid is affected much less by the analogue, and the inhibition 

 under these conditions was essentially negligible, even though nicotinic 

 acid is somewhat less effective than nicotinamide in promoting growth 

 of the organism. Inhibition of growth promoted by a preparation of co- 

 enzyme I was not only more intense, but also was not prevented by addi- 

 tional amounts of coenzyme I. It was concluded that with Staphylococ- 

 cus aureus, nicotinic acid is not used solely for synthesis of this coenzyme. 



With Proteus vulgaris, 64 growth promoted by nicotinamide was pre- 

 vented by 3-pyridinesulfonamide, but the analogue was less inhibitory 

 to Proteus vulgaris than to Staphylococcus aureus. The inhibitory effect 

 of the compound on growth changed with time and usually disappeared 

 within a few days. The analogue was less effective in preventing growth 

 stimulated by cozymase and was ineffective in preventing growth stimu- 

 lated by nicotinic acid. 



The toxicity of pyridine-3-sulfonamide for Streptobacterium plantarum 

 is prevented over a narrow range of concentrations by nicotinic acid, 

 nicotinamide, coenzyme I, 5-thiazolecarboxylic acid, and heavy metal 

 salts, particularly iron salts. 65 



3-Pyridinesulfonamide does not inhibit the growth of Escherichia 

 coli, 64 - 66 some strains of Proteus vulgaris, or the flagellate, Polytomella 

 caeca 66 



