Chitin, ƒÀ-(1, 4) linked N-acetylglucosamin
(GlcNAc) units, is an insoluble polysaccharide and is abundant in the marine
environment. Chitin is mainly derived from crustaceans such as shrimps
and crab shells and has received attention as a useful biomass. Chitinases
(EC 3.2.1.14), which hydrolyze the ƒÀ-1, 4-N-acetyl-glucosaminidic
linkages in a soluble chitin polymer, have been characterized in various
kinds of organisms such as yeast, fungi, bacteria and plants.
We have isolated and characterized Enterobacter sp. G-1
as a microorganism that secretes chitinases as described by Park
et
al (1) (2). Park describes the cloning, characterization, and transcriptional
analysis of the chitinaseA (chiA) gene encoding one of chitinases
from Enterobacter sp. G-1.
Chitosan is a polysaccharide consisting of ƒÀ-1, 4-linked D-glucosamine
residues, which partially replaced with N-acetyl-D-glucosamine.
Chitooligosaccharides produced by enzymatic hydrolysis of chitosan are
used as food additives, pharmaceuticals, and elicitors in plant cell culture.
The hydrolysis of glycosidic bonds of chitosan is catalyzed by chitosanase
(EC 3.2.1.132). Chitosanases are produced by many organisms, including
actinomycete, fungi, plants and bacteria. In plants, chitosanases have
been considered as pathogenesis-related proteins, which is involved in
defense mechanisms against pathogenic fungi. Bacterial chitosanases are
important for the maintenance of the ecological balance and have been used
to determine the mechanism of chitosan hydrolysis at both biochemical and
molecular levels.
Matsuebater chitosanotabidus 3001 that belongs to ƒÀ-subclass
of Proteobacterium was isolated from a soil of Matsue city as a
chitosanase producer. Biochemical properties of the purified chitosanaseA
from M. chitosanotabidus 3001 have been characterized, and the chitosanaseA
(choA) gene has been cloned (3).
We are analyzing glycosylhydrolase (especially, N-acetylglucosaminidase,
chitinase and chitosanase) using techniqnes of genetic engineering and
molecular biology.
References
(1) Park, J. K. et al, 1997, Purification and characterization
of the chitinase (ChiA) from Enterobacter sp. G-1, Biosic. Biotech.
Biochem., 61. 684.
(2) Park, J. K. et al, 1997, Molecular cloning, nucleotide sequencing,
and regulation of the chiA gene encoding one of chitinases from Enterobacter
sp. G-1., J. ferment. Bioengin., 84. 493.
(3) Park, J. K. et al, 1999. Purification, characterization,
and gene analysis of a chitosanase (ChoA) from Matsuebacter chitosanotabidus
3001. J. Bacteriol. 181. 6642.