Niacin Metabolism in Mycobacteria1,2

Abstract

Human tubercle bacilli, as compared with other mycobacteria, produce a large amount of in the culture medium (1). The niacin (2), which distinguishes human tubercle bacilli biochemically from other mycobacteria, is based on this difference in production. Albertson and Moat (3) reported that niacin-14C was formed from aspartic acid-14C and suggested that was formed by the condensation of a four-carbon dicarboxylic acid with a three-carbon compound. Konno and co-workers (4, 5), using cellfree extracts of mycobacteria, reported that quinolinic acid was a precursor of ribonucleotide (deamido-NMN). The enzyme activity that converts quinolinic acid to deamidoNMN was found to parallel production. Nakamura, Nishizuka, and Hayaishi (6), using a purified beef liver extract system, demonstrated the regulation of nicotinamide adenine dinucleotide (NAD) biosynthesis by adenosine triphosphate (ATP). In the absence of ATP, deamido-NMN is converted to ribonucleoside and eventually to niacin. However, when a sufficient amount of ATP is available, and ribonucleoside are utilized for the synthesis of deamido-NMN, and no accumulates. The production of excess by human strains of mycobacteria suggested that a similar mechanism might be operative, and the studies reported here were designed to test this hypothesis.