Isethionate formation from taurine in Chromohalobacter salexigens: purification of sulfoacetaldehyde reductase.
Bacterial generation of isethionate (2-hydroxyethanesulfonate) from taurine (2-aminoethanesulfonate) by anaerobic gut bacteria was established in 1980. That phenomenon in pure culture was recognized as a pathway of assimilation of taurine-nitrogen. Based on the latter work, we predicted from genome-sequence data that the marine gammaproteobacterium Chromohalobacter salexigens DSM 3043 would exhibit this trait. Quantitative conversion of taurine to isethionate, identified by mass spectrometry, was confirmed, and the taurine-nitrogen was recovered as cell material. An eight-gene cluster was predicted to encode the inducible vectorial, scalar and regulatory enzymes involved, some of which were known from other taurine pathways. The genes (Csal_0153-Csal_0156) encoding a putative ATP-binding-cassette (ABC) transporter for taurine (TauAB(1)B(2)C) were shown to be inducibly transcribed by reverse transcription (RT-) PCR. An inducible taurine : 2-oxoglutarate aminotransferase [EC 2.6.1.55] was found (Csal_0158); the reaction yielded glutamate and sulfoacetaldehyde. The sulfoacetaldehyde was reduced to isethionate by NADPH-dependent sulfoacetaldehyde reductase (IsfD), a member of the short-chain alcohol dehydrogenase superfamily. The 27 kDa protein (SDS-PAGE) was identified by peptide-mass fingerprinting as the gene product of Csal_0161. The putative exporter of isethionate (IsfE) is encoded by Csal_0160; isfE was inducibly transcribed (RT-PCR). The presumed transcriptional regulator, TauR (Csal_0157), may autoregulate its own expression, typical of GntR-type regulators. Similar gene clusters were found in several marine and terrestrial gammaproteobacteria, which, in the gut canal, could be the source of not only mammalian, but also arachnid and cephalopod isethionate.
Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, CZ-16637 Prague, Czech Republic.|Department of Biology, The University, D-78457 Konstanz, Germany.
Zdeněk
Z
Krejčík
Institute of Biochemical Engineering, Saarland University, Box 50 11 50, D-66041 Saarbrücken, Germany.
Klaus
K
Hollemeyer
Agroscope Changins-Wädenswil ACW, Schloss, Postfach, CH-8820 Wädenswil, Switzerland.|Department of Biology, The University, D-78457 Konstanz, Germany.
Theo H M
THM
Smits
Department of Biology, The University, D-78457 Konstanz, Germany.
Alasdair M
AM
Cook
D000586:Amination; D001426:Bacterial Proteins / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D055353:Chromohalobacter / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D005798:Genes, Bacterial; D007513:Isethionic Acid / Q000378:metabolism*; D007527:Isoenzymes / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D007536:Isomerism; D041121:Klebsiella oxytoca / Q000378:metabolism; D053544:Marinomonas / Q000378:metabolism; D053858:Metabolic Networks and Pathways / Q000235:genetics; D005810:Multigene Family; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013654:Taurine / Q000378:metabolism*
D001426:Bacterial Proteins; D007527:Isoenzymes; D013654:Taurine; D007513:Isethionic Acid