Dissimilation of cysteate via 3-sulfolactate sulfo-lyase and a sulfate exporter in Paracoccus pantotrophus NKNCYSA.
Paracoccus pantotrophus NKNCYSA utilizes (R)-cysteate (2-amino-3-sulfopropionate) as a sole source of carbon and energy for growth, with either nitrate or molecular oxygen as terminal electron acceptor, and the specific utilization rate of cysteate is about 2 mkat (kg protein)(-1). The initial degradative reaction is catalysed by an (R)-cysteate : 2-oxoglutarate aminotransferase, which yields 3-sulfopyruvate. The latter was reduced to 3-sulfolactate by an NAD-linked sulfolactate dehydrogenase [3.3 mkat (kg protein)(-1)]. The inducible desulfonation reaction was not detected initially in cell extracts. However, a strongly induced protein with subunits of 8 kDa (alpha) and 42 kDa (beta) was found and purified. The corresponding genes had similarities to those encoding altronate dehydratases, which often require iron for activity. The purified enzyme could then be shown to convert 3-sulfolactate to sulfite and pyruvate and it was termed sulfolactate sulfo-lyase (Suy). A high level of sulfite dehydrogenase was also induced during growth with cysteate, and the organism excreted sulfate. A putative regulator, OrfR, was encoded upstream of suyAB on the reverse strand. Downstream of suyAB was suyZ, which was cotranscribed with suyB. The gene, an allele of tauZ, encoded a putative membrane protein with transmembrane helices (COG2855), and is a candidate to encode the sulfate exporter needed to maintain homeostasis during desulfonation. suyAB-like genes are widespread in sequenced genomes and environmental samples where, in contrast to the current annotation, several presumably encode the desulfonation of 3-sulfolactate, a component of bacterial spores.
Rein
Ulrike
U
Department of Biology, The University, D-78457 Konstanz, Germany.
Gueta
Ronnie
R
Department of Biology, The University, D-78457 Konstanz, Germany.
Denger
Karin
K
Department of Biology, The University, D-78457 Konstanz, Germany.
Ruff
Jürgen
J
Department of Biology, The University, D-78457 Konstanz, Germany.
Hollemeyer
Klaus
K
Institute of Biochemical Engineering, Saarland University, Box 50 11 50, D-66041 Saarbrücken, Germany.
Cook
Alasdair M
AM
Department of Biology, The University, D-78457 Konstanz, Germany.
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003470:Culture Media; D003544:Cysteic Acid / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D007773:Lactates / Q000378:metabolism*; D008190:Lyases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D042084:Paracoccus pantotrophus / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D013431:Sulfates / Q000378:metabolism*
D001426:Bacterial Proteins; D003470:Culture Media; D007773:Lactates; D013431:Sulfates; D003544:Cysteic Acid; D008190:Lyases