The biological activity of pantolactone and pantoic acid.

As far as we are aware, no distinction has been made between the biological activity of pantolactone (CL, y-dihydroxy-p, fl-dimethylbutyrolactone) and pantoic acid or its ion.1 In connection with studies on the antagonistic action of pantoyltaurine on salicylate inhibition of Escherichia coli 2 we have observed that pantoic acid, or, more properly, the pantoate ion, is more active than pantolactone. In low concentrations, salicylic acid is thought to inhibit growth of bacteria which synthesize pantothenate (e.g., Escherichia coli) by preventing the formation of pantoic acid or pantolactone (2). If such bacteria are supplied with pantothenic acid, pantoate, or pantolactone, the inhibitory effect of salicylate is nullified. Presumably, the pantoate or pantola&one is used to synthesize pantothenic acid. The fact that pantoate is more active than pantolactone in antagonizing salicylate indicates that pantoate is more readily utilized than pantolactone for the synthesis of pantothenic acid. This suggests that the immediate precursor in the biological synthesis of pantothenic acid is pantoic acid or pantoate rather than pantolactone.