title: CysK from Lactobacillus casei encodes a protein with O-acetylserine sulfhydrylase and cysteine desulfurization activity.
abstract: A gene encoding an O-acetyl-L-serine sulfhydrylase (cysK) was cloned from Lactobacillus casei FAM18110 and expressed in Escherichia coli. The purified recombinant enzyme synthesized cysteine from sulfide and O-acetyl-L-serine at pH 5.5 and pH 7.4. At pH 7.4, the apparent K(M) for O-acetyl-L-serine (OAS) and sulfide were 0.6 and 6.7 mM, respectively. Furthermore, the enzyme showed cysteine desulfurization activity in the presence of dithiothreitol at pH 7.5, but not at pH 5.5. The apparent K(M) for L-cysteine was 0.7 mM. The synthesis of cystathionine from homocysteine and serine or OAS was not observed. When expressed in a cysMK mutant of Escherichia coli, the cloned gene complemented the cysteine auxotrophy of the mutant. These findings suggested that the gene product is mainly involved in cysteine biosynthesis in L. casei. Quantitative real-time PCR and a mass spectrometric assay based on selected reaction monitoring demonstrated that L. casei FAM18110 is constitutively overexpressing cysK.
authors: Agroscope Liebefeld-Posieux Research Station ALP, Bern, Switzerland.
authors: Biljana
authors: B
authors: Bogicevic
authors: Hélène
authors: H
authors: Berthoud
authors: Reto
authors: R
authors: Portmann
authors: Leo
authors: L
authors: Meile
authors: Stefan
authors: S
authors: Irmler
mesh_terms: D013437:Carbon-Sulfur Lyases / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D003545:Cysteine / Q000378:metabolism*; D003547:Cysteine Synthase / Q000235:genetics / Q000378:metabolism*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D015870:Gene Expression; D020869:Gene Expression Profiling; D005816:Genetic Complementation Test; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D007780:Lacticaseibacillus casei / Q000201:enzymology* / Q000235:genetics; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D060888:Real-Time Polymerase Chain Reaction; D011994:Recombinant Proteins / Q000235:genetics / Q000302:isolation & purification; D017422:Sequence Analysis, DNA; D012694:Serine / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: D004269:DNA, Bacterial; D011994:Recombinant Proteins; D012694:Serine; D003547:Cysteine Synthase; D013437:Carbon-Sulfur Lyases; C080546:cysteine desulfurase; C043943:O-acetylserine; D003545:Cysteine