Characterization of 38kDa and 42kDa chitinase isozymes from the liver of Japanese common Squid Todarodes pacificus

• Published in: Fisheries science Vol. 68; no. 3; pp. 603 - 609
• Main Authors: Matsumiya, Masahiro, Miyauchi, Kouji, Mochizki, Atsushi
• Format: Journal Article
• Language: English
• Published: 2002
• Subjects: Todarodes pacificus
• ISSN: 0919-9268
• DOI: 10.1046/j.1444-2906.2002.00467.x

Characterization was investigated on the 38kDa and 42kDa chitinase (EC3.2.1.14)isozymes from the liver of Japanese common squid Todarodes pacificus. Optimum pH toward colloidal chitin was observed at pH 3.0 for the 38 kDa chitinase, and pH 3.0 and 9.0 for the 42 kDa chitinase. K sub(m) and k sub(cat) of the 38 kDa and 42 kDa chitinases toward a longer substrate, glycol chitin, were 0.071mg/mL and 1.22/s, and 0.074mg/mL and 0.196/s, respectively. Alternatively, strong substrate inhibition of both chitinases were observed toward a short substrate, N-acetylchitopentaose (GlcNAc sub(5)). Both chitinases decomposed not only chitin but also chitosan (D. A. 95%). The cleavage pattern and reaction rate were investigated using N-acetylchitooligosaccharides (GlcNAc sub(n), n=2-6). Both chitinases hydrolyzed GlcNAc sub(n) (n=4, 5, and 6). The release of GlcNAc was not observed. The speed of the reaction was observed to be in the following order: GlcNAc sub(4)>GlcNAc sub(5)>GlcNAc sub(6) for the 38kDa chitinase, and GlcNAc sub(6)> GlcNAc sub(5)> GlcNAc sub(4) for the 42kDa chitinase. Both the chitinases released p-nitrophenol from p-nitrophenyl GlcNAc sub(n) (n=2, 3, and 4). N-terminal amino acid sequences of the 38 kDa and 42 kDa chitinases were YLLSXYFTNWSQYRPGAGKYFPQNI and EYRKVXYYTNWSQYREVPAKFFPEN, respectively.