title: The third chitinase gene (chiC) of Serratia marcescens 2170 and the relationship of its product to other bacterial chitinases.
abstract: The third chitinase gene (chiC) of Serratia marcescens 2170, specifying chitinases C1 and C2, was identified. Chitinase C1 lacks a signal sequence and consists of a catalytic domain belonging to glycoside hydrolase family 18, a fibronectin type III-like domain (Fn3 domain) and a C-terminal chitin-binding domain (ChBD). Chitinase C2 corresponds to the catalytic domain of C1 and is probably generated by proteolytic removal of the Fn3 and ChBDs. The loss of the C-terminal portion reduced the hydrolytic activity towards powdered chitin and regenerated chitin, but not towards colloidal chitin and glycol chitin, illustrating the importance of the ChBD for the efficient hydrolysis of crystalline chitin. Phylogenetic analysis showed that bacterial family 18 chitinases can be clustered in three subfamilies which have diverged at an early stage of bacterial chitinase evolution. Ser. marcescens chitinase C1 is found in one subfamily, whereas chitinases A and B of the same bacterium belong to another subfamily. Chitinase C1 is the only Ser. marcescens chitinase that has an Fn3 domain. The presence of multiple, divergent, chitinases in a single chitinolytic bacterium is perhaps necessary for efficient synergistic degradation of chitin.
authors.affiliation: Department of Biosystem Science, Graduate School of Science and Technology, Niigata University, 8050 Ikarashi-2, Niigata 950-2181, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Suzuki
authors.forename: M
authors.initials: M
authors.lastname: Taiyoji
authors.forename: N
authors.initials: N
authors.lastname: Sugawara
authors.forename: N
authors.initials: N
authors.lastname: Nikaidou
authors.forename: B
authors.initials: B
authors.lastname: Henrissat
authors.forename: T
authors.initials: T
authors.lastname: Watanabe
mesh_terms: D000595:Amino Acid Sequence; D001407:Bacillus / Q000201:enzymology; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D002688:Chitinases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D019143:Evolution, Molecular; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D008969:Molecular Sequence Data; D010802:Phylogeny; D017433:Protein Structure, Secondary; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012706:Serratia marcescens / Q000201:enzymology* / Q000235:genetics*; D013305:Streptomyces griseus / Q000201:enzymology; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D007527:Isoenzymes; D002688:Chitinases; C101644:chitinase C-1