title: Nucleoside diphosphate kinase-like activity in adenylate kinase of Mycobacterium tuberculosis.
abstract: Ak (adenylate kinase) is a ubiquitous enzyme that catalyses a reversible high-energy phosphoryl-transfer reaction between ATP and AMP to form ADP. In the present study, the Ak gene (adk) of Mycobacterium tuberculosis was cloned, expressed in Escherichia coli and purified as a glutathione S-transferase fusion protein. Purified Ak converted AMP into ADP in the presence of [gamma-32P]ATP or [gamma-32P]GTP. Replacement of arginine-88 of adk with glycine resulted in the loss of enzymic activity. The purified protein also showed Ndk (nucleoside diphosphate kinase)-like activity as it transferred terminal phosphate from [gamma-32P]ATP to all nucleoside diphosphates, converting them into corresponding triphosphates. However, Ndk-like activity of Ak was not observed with [gamma-32P]GTP. Immunoblot analysis of various cellular fractions of M. tuberculosis H37Rv revealed that Ak is a cytoplasmic protein. The dual activity of Ak as both nucleoside mono- and di-phosphate kinases suggested that this enzyme may have a role in RNA and DNA biosynthesis in addition to its role in intracellular nucleotide metabolism.
authors.affiliation: Institute of Genomics and Integrative Biology, Mall Road, Delhi-110007, India.
authors.forename: Laxman S
authors.initials: LS
authors.lastname: Meena
authors.forename: Puneet
authors.initials: P
authors.lastname: Chopra
authors.forename: R S
authors.initials: RS
authors.lastname: Bedwal
authors.forename: Yogendra
authors.initials: Y
authors.lastname: Singh
mesh_terms: D000263:Adenylate Kinase / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001120:Arginine / Q000737:chemistry; D005822:Genetic Vectors; D008969:Molecular Sequence Data; D009169:Mycobacterium tuberculosis / Q000737:chemistry / Q000201:enzymology*; D009701:Nucleoside-Diphosphate Kinase / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D010957:Plasmids / Q000235:genetics
chemical_list: D001120:Arginine; D000263:Adenylate Kinase; D009701:Nucleoside-Diphosphate Kinase