| Summary: | Glaciozyma antarctica is a psychrophilic yeast that was isolated from the surface of Antarctic sea ice. A key adaptation of psychrophilic microorganisms is to synthesize cold‐active enzymes for survival at low temperatures. In this study, the full‐length cDNA encoding Exo‐β‐glucanase (GaExg55) from G. antarctica PI12 was amplified by reverse‐transcription polymerase chain reaction (RT‐PCR). The cDNA encoded a 480‐residue polypeptide with a putative signal peptide of 20 residues. Subsequently, the novel GaExg55 was expressed in E. coli and purified with nickel affinity chromatography as an approximately 55 kDa protein. The biochemical characterization of purified recombinant GaExg55 (rGaExg55) revealed typical cold‐active enzyme characteristics, such as maximal activity at 20 °C and pH 8.0. The K m and V max values of the enzyme using laminarin as the substrate were 10.04 mg mL −1 and 14.12 U mg −1 , respectively. An analysis of the three‐dimensional structure of the enzyme was carried out using MODELLER9v16 and compared with homologous mesophilic exo‐β‐1,3‐glucanase. The results of the comparative structural study revealed that the psychrophilic GaExg55 contains longer loops, fewer hydrogen bonds and salt bridges, and a higher total solvent‐accessible surface area which enhanced the protein flexibility for high catalytic efficiency at low temperatures. Support or Funding Information This research was supported by a research grant from the Ministry of Science Technology and Innovation (MOSTI), Malaysia under the research grants 10‐05‐16‐MB002 and 02‐05‐20‐SF0007. This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .
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