title: Molecular genetics and biochemistry of N-acetyltaurine degradation by Cupriavidus necator H16.
abstract: Cupriavidus necator H16 (DSM 428), whose genome has been sequenced, was found to degrade N-acetyltaurine as a sole source of carbon and energy for growth. Utilization of the compound was quantitative. The degradative pathway involved an inducible N-acetyltaurine amidohydrolase (NaaS), which catalysed the cleavage of N-acetyltaurine to acetate and taurine. The degradation of the latter compound is via an inducible, degradative pathway that involves taurine dehydrogenase [EC 1.4.2.-], sulfoacetaldehyde acetyltransferase [EC 2.3.3.15], phosphotransacetylase [EC 2.4.1.8], a sulfite exporter [TC 9.A.29.2.1] and sulfite dehydrogenase [EC 1.8.2.1]. Induction of the expression of representative gene products, encoded by at least four gene clusters, was confirmed biochemically. The acetate released by NaaS was activated to acetyl-CoA by an inducible acetate-CoA ligase [EC 6.2.1.1]. NaaS was purified to homogeneity; it had a K(m) value of 9.4 mM for N-acetyltaurine, and it contained tightly bound Zn and Fe atoms. The denatured enzyme has a molecular mass of about 61 kDa (determined by SDS-PAGE) and the native enzyme was apparently monomeric. Peptide-mass fingerprinting identified the locus tag as H16_B0868 in a five-gene cluster, naaROPST (H16_B0865-H16_B0869). The cluster presumably encodes a LysR-type transcriptional regulator (NaaR), a membrane protein (NaaO), a solute : sodium symporter-family permease [TC 2.A.21] (NaaP), the metal-dependent amidohydrolase (NaaS) and a putative metallochaperone (COG0523) (NaaT). Reverse-transcription PCR indicated that naaOPST were inducibly transcribed.
authors.affiliation: Department of Biology, The University, D-78457 Konstanz, Germany.
authors.forename: Karin
authors.initials: K
authors.lastname: Denger
authors.affiliation: Department of Biology, The University, D-78457 Konstanz, Germany.
authors.forename: Sabine
authors.initials: S
authors.lastname: Lehmann
authors.affiliation: Department of Biology, The University, D-78457 Konstanz, Germany.
authors.forename: Alasdair M
authors.initials: AM
authors.lastname: Cook
mesh_terms: D000581:Amidohydrolases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D020118:Cupriavidus necator / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D007700:Kinetics; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D056511:Metallochaperones / Q000235:genetics / Q000378:metabolism; D005810:Multigene Family; D013654:Taurine / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D026901:Membrane Transport Proteins; D056511:Metallochaperones; C083076:acetyltaurine; D013654:Taurine; D000581:Amidohydrolases