Inhibition of nicotinamide deamidase from Micrococcus lysodeikticus by analogues of nicotinamide

Abstract

1. 1. Nicotinamide deamidase from Micrococcus lysodeikticus was competitively inhibited by a large number of structural analogues of nicotinamide. 2. 2. Of 59 analogues tested, the most potent inhibitors, with inhibitor constants ( K i) less than 10 −5 M, in decreasing order of potency, were: 3-pyridinecarboxaldehyde, nicotinic acid hydrazide, 4-aminonicotinamide, 3-cyanopyridine, 3-pyridylcarbinol, 3-aminomethylpyridine, and 3-pyridinealdoxime. Moderately active inhibitors ( K i between 10 −3 M and 10 −5 M), in decreasing order of potency included: thionicotinamide, 3-acetylpyridine, 5-methylnicotinamide, pyrazinamide, nicotinylhydroxamic acid, nipecotamide, 3-chloropyridine, 3-(3-pyridyl)-1-propanol, 3-pyridineacetonitrile, o-bromobenzamide, and isoniazid. 3. 3. The pyridine nitrogen and the carbonyl carbon of nicotinamide are involved in substrate-enzyme binding, and the enzyme exhibits steric hindrance in binding nicotinamide analogues with substituents at the 1-, 5-, and 6-positions of the pyridine ring.