The Journal of General and Applied Microbiology
Online ISSN : 1349-8037
Print ISSN : 0022-1260
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Enzymatic and molecular characterization of an acidic and thermostable chitinase 1 from Streptomyces thermodiastaticus HF 3-3
Keitaro TakeHidehisa FujikiWasana SuyothaJunji HayashiKazuyoshi TakagiShigekazu YanoMamoru Wakayama
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2018 Volume 64 Issue 4 Pages 190-197

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Abstract

Chitinase 1 (Chi1) is an acidic and thermostable hydrolytic enzyme capable of the breakdown of chitin, a resilient biopolymer that is the primary building block of fungi cell walls and marine exoskeletons. In this study, Chi1 was purified from the bacterium Streptomyces thermodiastaticus HF 3-3, and its properties were carefully characterized. The molecular mass of Chi1 was estimated to be approximately 46 kDa and, through sequencing, its N-terminal amino acid sequence was identified as ADSGKVKL. Although the optimal operating temperature and pH for Chi1 were determined to be 65°C and pH 5.5, respectively, the purified enzyme was stable over wide pH (1.5–9) and temperature ranges. Moreover, Chi1 retained 87% of its activity in the presence of 15% NaCl. While Chi1 activity was inhibited by Ag+ and Mn2+, other chemicals tested had no significant effect on its enzymatic activity. The Km and Vmax values of Chi1 for the substrate colloidal chitin were 1.23 ± 0.7 mg/mL and 6.33 ± 1.0 U/mg, respectively. Thin-layer chromatography analysis of the enzymatic reaction end products mainly detected diacetylchitobiose. We also cloned the Chi1 gene and purified the recombinant protein; the properties of the recombinant enzyme were nearly identical to those of the native enzyme. Therefore, Chi1 purified from S. thermodiastaticus HF 3-3 is unique, as it is highly stable under broad range of pH values, temperatures, and chemical exposures. Combined, these properties make this enzyme attractive for use in the industrial bioconversion of chitin.

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© 2018, Applied Microbiology, Molecular and Cellular Biosciences Research Foundation
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