Inhibition and activation studies of histidine decarboxylase from lactobacillus 30a by imidazolidine 4-one derivatives using a pH-stat technique
Pyruvate depedent histidine decarboxylase from Lactobacillus 30a (EC 188.8.131.52) was used and IC50 values were determined for four new imidazolidine 4-one derivatives as inhibitors of the enzyme. 2,2-dimethyl-5-phenyl imidazolidine-4-one (DMPI), 2-ethyl-2-methyl- 5-phenyl imidazolidine-4-one (EMPI), 5-Phenyl-1,3-diazaspiro [4,4] nonane 4-one (PDAN) and 5-phenyl-1,3-diazaspiro [4,5] decane-4-one (PDAD) showed decreases in inhibitory activity as the size of C2 substituent on imidazolidine 4-one derivatives increased. The activation of enzyme occurred with the compounds that contained largest substituent. Correlations existed between log IC50 and the molecular diameter as established by computer aided estimations.