Inhibition of Nicotinamidase by Nicotinamide Adenine Dinucleotide

• Published in: The Journal of biological chemistry 1971-07, Vol.246 (13), p.4334-4339
• Main Authors: Calbreath, D F, Joshi, J G
• Format: Article
• Language: English
• Subjects: Acetylesterase; Adenine Nucleotides; Amidohydrolases - antagonists & inhibitors; Animals; Bacillus - enzymology; Chloromercuribenzoates; Chromatography; Chromatography, DEAE-Cellulose; Clostridium - enzymology; Escherichia coli - enzymology; Fatty Acids; Feedback; Hydrogen-Ion Concentration; Hydroxyapatites; Kinetics; Micrococcus - enzymology; Microsomes, Liver - enzymology; Molecular Weight; NAD; Niacinamide; Nucleoside Diphosphate Sugars; Nucleotides; Pentosephosphates; Pyridines; Rabbits; Saccharomyces - enzymology; Species Specificity; Thyroxine; Time Factors; Urea
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(18)62089-7

Feedback inhibition by NAD was shown with the nicotinamidases of a number of microorganisms. The purified enzyme from Fleischmann's yeast was found to have a molecular weight of 110,000 and consist of presumably identical subunits with a molecular weight of 26,000. A Lineweaver-Burk plot of the NAD inhibition is concave upward at low concentrations of NAD; at 6 m m NAD, the linear plot is that of a competitive inhibitor with an apparent K i of 7 x 10 -4 m . Other competitive inhibitors include NMN ( K i = 6.5 x 10 -5 m ) and 3-acetylpyridine ( K i = 4.6 x 10 -4 m ). ADP, ADP-ribose, and PP-ribose-P were all noncompetitive inhibitors with K i values of approximately 1 x 10 -4 m . Inactivation of enzyme by urea can be prevented or partially reversed by the presence of NAD, NMN, or 3-acetylpyridine. The inactivation by urea was time-dependent and could be reversed by subsequent addition of substrate. p -Chloromercuribenzoate inhibition is competitive, with an apparent K i of 2 x 10 -7 m , and was reversed by dithiothreitol. The properties of the nicotinamidases of yeast and rabbit liver microsomes differ markedly.