title: The biological function of the bacterial isochorismatase-like hydrolase SttH.
abstract: The streptothricin hydrolase (SttH), which is a member of the isochorismatase-like hydrolase (ILH) super-family, catalyzes the hydrolysis of the streptolidine lactam group in streptothricin (ST) antibiotics, thereby inactivating them. In this study we identified a novel homologous gene (sttH-sn) and sequenced the flanking regions of the sttH and sttH-sn genes. The organization of genes around the sttH, sttH-sn, and ILH genes revealed that a number of the genes were clustered with genes encoding oxidoreductases with molybdopterin binding subunits, suggesting that the true role of these gene products (SttHs and a number of ILHs) might have to do with the chemical modification of molybdopterin, rather than ST-resistance. In addition, mutant enzymes were constructed in which Ser was substituted for highly conserved Cys-176 and Cys-158 of SttH and SttH-sn respectively, and no enzyme activities were detected. Thus, biochemically, these ILHs were found to be "cysteine hydrolases."
authors.affiliation: Department of Bioscience, Fukui Prefectural University, Yoshida-gun, Fukui, Japan.
authors.forename: Chitose
authors.initials: C
authors.lastname: Maruyama
authors.forename: Yoshimitsu
authors.initials: Y
authors.lastname: Hamano
mesh_terms: D000595:Amino Acid Sequence; D055162:Biocatalysis; D003001:Cloning, Molecular; D006867:Hydrolases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006868:Hydrolysis; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D017422:Sequence Analysis, DNA; D013302:Streptomyces / Q000201:enzymology*; D013309:Streptothricins / Q000378:metabolism*
chemical_list: D013309:Streptothricins; D006867:Hydrolases; C064012:isochorismatase