Identification and functional analysis of the Saccharomyces cerevisiae nicotinamidase gene, PNC1

Abstract

Nicotinamidase (NAMase) from the budding yeast, Saccharomyces cerevisiae, was purified by Ni 2+ affinity chromatography and gel filtration. N‐terminal microsequencing revealed sequence identity with a hypothetical polypeptide encoded by the yeast YGL037C open reading frame sharing 30% sequence identity with Escherichia coli pyrazinamidase/nicotinamidase. A yeast strain in which the NAMase gene, hereafter named PNC1, was deleted shows a decreased intracellular NAD+ concentration, consistent with the loss of NAMase activity in the null mutant. In wild‐type strains, NAMase activity is stimulated during the stationary phase of growth, by various hyperosmotic shocks or by ethanol treatment. Using a PPNC1::lacZ gene fusion, we have shown that this stimulation of NAMase activity results from increased levels of the protein and requires stress response elements in the 5′ non‐coding region of PNC1. These results suggest that NAMase helps yeast cells to adapt to various stress conditions and nutrient depletion, most likely via the activation of NAD‐dependent biological processes. Copyright © 2002 John Wiley & Sons, Ltd.