Marine Drugs (Dec 2022)

A Novel κ-Carrageenase from Marine Bacterium <i>Rhodopirellula sallentina</i> SM41: Heterologous Expression, Biochemical Characterization and Salt-Tolerance Mechanism Investigation

  • Yong-Hui Zhang,
  • Yi-Ying Chen,
  • Xiao-Yan Zhuang,
  • Qiong Xiao,
  • Jun Chen,
  • Fu-Quan Chen,
  • Qiu-Ming Yang,
  • Hui-Fen Weng,
  • Bai-Shan Fang,
  • An-Feng Xiao

DOI
https://doi.org/10.3390/md20120783
Journal volume & issue
Vol. 20, no. 12
p. 783

Abstract

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κ-carrageenases are members of the glycoside hydrolase family 16 (GH16) that hydrolyze sulfated galactans in red algae, known as κ-carrageenans. In this study, a novel κ-carrageenase gene from the marine bacterium Rhodopirellula sallentina SM41 (RsCgk) was discovered via the genome mining approach. There are currently no reports on κ-carrageenase from the Rhodopirellula genus, and RsCgk shares a low identity (less than 65%) with κ- carrageenase from other genera. The RsCgk was heterologously overexpressed in Escherichia coli BL21 and characterized for its enzymatic properties. RsCgk exhibited maximum activity at pH 7.0 and 40 °C, and 50% of its initial activity was retained after incubating at 30 °C for 2 h. More than 70% of its activity was maintained after incubation at pH 6.0–8.0 and 4 °C for 24 h. As a marine derived enzyme, RsCgk showed excellent salt tolerance, retaining full activity in 1.2 M NaCl, and the addition of NaCl greatly enhanced its thermal stability. Mass spectrometry analysis of the RsCgk hydrolysis products revealed that the enzyme had high degradation specificity and mainly produced κ-carrageenan disaccharide. Comparative molecular dynamics simulations revealed that the conformational changes of tunnel-forming loops under salt environments may cause the deactivation or stabilization of RsCgk. Our results demonstrated that RsCgk could be utilized as a potential tool enzyme for efficient production of κ-carrageenan oligosaccharides under high salt conditions.

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