A novel goose-type lysozyme gene with chitinolytic activity from the moderately thermophilic bacterium Ralstonia sp. A-471: cloning, sequencing, and expression

Appl Microbiol Biotechnol. 2009 Jan;81(6):1077-85. doi: 10.1007/s00253-008-1676-y. Epub 2008 Sep 30.

Abstract

In this study, we cloned the gene encoding goose-type (G-type) lysozyme with chitinase (Ra-ChiC) activity from Ralstonia sp. A-471 genomic DNA library. This is the first report of another type of chitinase after the previously reported chitinases ChiA (Ra-ChiA) and ChiB (Ra-ChiB) in the chitinase system of the moderately thermophilic bacterium, Ralstonia sp. A-471 and also the first such data in Ralstonia sp. G-type lysozyme gene. It consisted of 753 bp nucleotides, which encodes 251 amino acids including a putative signal peptide. This ORF was modular enzyme composed of a signal sequence, chitin-binding domain, linker, and catalytic domain. The catalytic domain of Ra-ChiC showed homologies to those of G-type lysozyme (glycoside hydrolases (GH) family 23, 16.8%) and lysozyme-like enzyme from Clostridium beijerincki (76.1%). Ra-ChiC had activities against ethylene glycol chitin, carboxyl methyl chitin, and soluble chitin but not against the cell wall of Micrococcus lysodeikticus. The enzyme produced alpha-anomer by hydrolyzing beta-1,4-glycosidic linkage of the substrate, indicating that the enzyme catalyzes the hydrolysis through an inverting mechanism. When N-acetylglucosamine hexasaccharide [(GlcNAc)6] was hydrolyzed by the enzyme, the second and third glycosidic linkage from the non-reducing end were split producing (GlcNAc)2 + (GlcNAc)4 and (GlcNAc)3 + (GlcNAc)3 of almost the same concentration in the early stage of the reaction. The G-type lysozyme hydrolyzed (GlcNAc)6 in an endo-splitting manner, which produced (GlcNAc)3 + (GlcNAc)3 predominating over that to (GlcNAc)2 + (GlcNAc)4. Thus, Ra-ChiC was found to be a novel enzyme in its structural and functional properties.

MeSH terms

  • Amino Acid Sequence / genetics
  • Base Sequence
  • Chitin / metabolism*
  • Cloning, Molecular
  • DNA, Bacterial / chemistry
  • DNA, Bacterial / genetics
  • Gene Expression
  • Molecular Sequence Data
  • Muramidase / genetics
  • Muramidase / isolation & purification
  • Muramidase / metabolism*
  • Open Reading Frames
  • Protein Sorting Signals
  • Protein Structure, Tertiary
  • Ralstonia / enzymology*
  • Sequence Analysis, DNA
  • Sequence Homology, Amino Acid
  • Substrate Specificity

Substances

  • DNA, Bacterial
  • Protein Sorting Signals
  • Chitin
  • Muramidase

Associated data

  • GENBANK/AB445458