Characterization of a Novel Thermostable O-Acetylserine Sulfhydrylase from Aeropyrum pernix K1
AUTOR(ES)
Mino, Koshiki
FONTE
American Society for Microbiology
RESUMO
An O-acetylserine sulfhydrylase (OASS) from the hyperthermophilic archaeon Aeropyrum pernix K1, which shares the pyridoxal 5′-phosphate binding motif with both OASS and cystathionine β-synthase (CBS), was cloned and expressed by using Escherichia coli Rosetta(DE3). The purified protein was a dimer and contained pyridoxal 5′-phosphate. It was shown to be an enzyme with CBS activity as well as OASS activity in vitro. The enzyme retained 90% of its activity after a 6-h incubation at 100°C. In the O-acetyl-l-serine sulfhydrylation reaction, it had a pH optimum of 6.7, apparent Km values for O-acetyl-l-serine and sulfide of 28 and below 0.2 mM, respectively, and a rate constant of 202 s−1. In the l-cystathionine synthetic reaction, it showed a broad pH optimum in the range of 8.1 to 8.8, apparent Km values for l-serine and l-homocysteine of 8 and 0.51 mM, respectively, and a rate constant of 0.7 s−1. A. pernix OASS has a high activity in the l-cysteine desulfurization reaction, which produces sulfide and S-(2,3-hydroxy-4-thiobutyl)-l-cysteine from l-cysteine and dithiothreitol.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=151494Documentos Relacionados
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