Purification and characterization of a 56 kDa chitinase isozyme (PaChiB) from the stomach of the silver croaker, Pennahia argentatus.

A 56 kDa chitinase isozyme (PaChiB) was purified from the stomach of the silver croaker Pennahia argentatus. The optimum pH and pH stability of PaChiB were observed in an acidic pH range. When N-acetylchitooligosaccharides ((GlcNAc)n, n=2 -6) were used as substrates, PaChiB degraded (GlcNAc)4 -6 and produced (GlcNAc)2,3. It degraded (GlcNAc)5 to produce (GlcNAc)2 (23.2%) and (GlcNAc)3 (76.8%). The ability to degrade p-nitrophenyl N-acetylchitooligosaccharides (pNp-(GlcNAc)n, n=2 -4) fell in the following order: pNp-(GlcNAc)3≫ pNp-(GlcNAc)2 pNp-(GlcNAc)4. Based on these results, we concluded that PaChiB is an endo-type chitinolytic enzyme, and that it preferentially hydrolyzes the third glycosidic bond from the non-reducing end of (GlcNAc)n. Activity toward crystalline α- and ß-chitin was activated at 124%-185% in the presence of 0.5 M NaCl. PaChiB exhibited markedly high substrate specificity toward crab-shell α-chitin.

Purification and characterization of chitinase from the stomach of silver croaker Pennahia argentatus.

A chitinase was purified from the stomach of a fish, the silver croaker Pennahia argentatus, by ammonium sulfate fractionation and column chromatography using Chitopearl Basic BL-03, CM-Toyopearl 650S, and Butyl-Toyopearl 650S. The molecular mass and isoelectric point were estimated at 42 kDa and 6.7, respectively. The N-terminal amino acid sequence showed a high level of homology with family 18 chitinases. The optimum pH of silver croaker chitinase toward p-nitrophenyl N-acetylchitobioside (pNp-(GlcNAc)2) and colloidal chitin were observed to be pH 2.5 and 4.0, respectively, while chitinase activity increased about 1.5- to 3-fold with the presence of NaCl. N-Acetylchitooligosaccharide ((GlcNAc)n, n = 2-6) hydrolysis products and their anomer formation ratios were analyzed by HPLC using a TSK-GEL Amide-80 column. Since the silver croaker chitinase hydrolyzed (GlcNAc)4-6 and produced (GlcNAc)2-4, it was judged to be an endo-type chitinase. Meanwhile, an increase in beta-anomers was recognized in the hydrolysis products, the same as with family 18 chitinases. This enzyme hydrolyzed (GlcNAc)5 to produce (GlcNAc)2 (79.2%) and (GlcNAc)3 (20.8%). Chitinase activity towards various substrates in the order pNp-(GlcNAc)n (n = 2-4) was pNp-(GlcNAc)2 >> pNp-(GlcNAc)4 > pNp-(GlcNAc)3. From these results, silver croaker chitinase was judged to be an enzyme that preferentially hydrolyzes the 2nd glycosidic link from the non-reducing end of (GlcNAc)n. The chitinase also showed wide substrate specificity for degrading alpha-chitin of shrimp and crab shell and beta-chitin of squid pen. This coincides well with the feeding habit of the silver croaker, which feeds mainly on these animals.

Purification and characterization of chitinase isozymes from a red algae, Chondrus verrucosus.

Three seaweed chitinase isozymes (Chi-A, B, and C) were purified from a red algae, Chondrus verrucosus. The molecular weights and isoelectric points were 24.5 kDa and 3.5 for Chi-A, 25.5 kDa and 4.6 for Chi-B, and 24.5 kDa and <3.5 for Chi-C. Optimum pH and temperature were observed at pH 2.0 at 80 degrees C for Chi-A and Chi-C, and at pH 1.0 and 70 degrees C for Chi-B. Toward N-acetylchitooligosaccharide (GlcNAc(n)) (n=2 to 6), Chi-A, B, and C hydrolyzed GlcNAc(5) and GlcNAc(6) and produced GlcNAc(n) (n=2 to 4). GlcNAc(n) (n=3, 4) with the reducing end-side of beta anomer was detected in the hydrolysis products. These results indicate that the reactions of Chi-A, B, and C for GlcNAc(n) were a retaining mechanism similar to that of family 18 chitinase. Toward crystalline chitins, Chi-A, B, and C degraded squid pen beta-chitin more than crab shell or shrimp shell alpha-chitin.