Chitinases (EC 18.104.22.168)  are enzymes that catalyze the hydrolysis of the
β-1,4-N-acetyl-D-glucosamine linkages in chitin polymers. From the view
point of sequence similarity chitinases belong to either family 18 or 19 in
the classification of glycosyl hydrolases [2,E1]. Chitinases of family 18
(also known as classes III or V) groups a variety of proteins:
a) Chitinases from:
- Prokaryotes such as Alteromonas, Bacillus, Serratia, Streptomyces, etc.
- Plants such as Arabidopsis, cucumber, bean, tobacco, etc.
- Fungi such as Aphanocladium, Rhizopus, Saccharomyces, etc.
- Nematode (Brugia malayi).
- Insects (Manduca sexta).
- Baculoviruses (Autographa Californica Nuclear Polyhedrosis virus).
b) Other proteins:
- Hevamine, a rubber tree protein with chitinase and lysozyme activities.
- Kluyveromyces lactis killer toxin alpha subunit, which acts as a chitinase.
- Flavobacterium and Streptomyces endo-beta-N-acetylglucosaminidases (EC 3.2.
- Mammalian di-N-acetylchitobiase which is involved in the degradation of
- Human cartilage glycoprotein Gp-39.
- Jack bean concanavalin B (conB), a protein that has lost its catalytic
Site directed mutagenesis experiments  and crystallographic data [4,5] have
shown that a conserved glutamate is involved in the catalytic mechanism and
probably acts as a proton donor. This glutamate is at the extremity of the
best conserved region in these proteins.
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