Journal
ENZYME AND MICROBIAL TECHNOLOGY
Volume 127, Issue -, Pages 22-31Publisher
ELSEVIER SCIENCE INC
DOI: 10.1016/j.enzmictec.2019.04.006
Keywords
beta-Agarase; Mutagenesis; Thermo-stability; Thermal deactivation kinetics; Hydrolysis kinetics
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Funding
- Natural Science Foundation of Fujian Province [2017J01446]
- National Natural Science Foundation of China [31500673]
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The recombinant rAgaZC-1 was a family GH50 beta-agarase from Vibrio sp. ZC-1 (CICC 24670). In this paper, the mutant D622G (i.e., mutate the aspartic acid at position 622 to glycine) had better thermo-stability than rAgaZC1, showing 1.5 degrees C higher T-50(10) (the temperature at which the half-time is 10 min) and 4-folds of half-time at 41 degrees C, while they had almost same optimum temperature (38.5 degrees C), optimum pH (pH6.0) and catalytic efficiency. Thermal deactivation kinetical analysis showed that D622G had higher activation energy for deactivation, enthalpy and Gibbs free energy than rAgaZC-1, indicating that more energy is required by D622G for deactivation. Substrate can protect agarase against thermal inactivation, especially D622G. Hence the yield of agarose hydrolysis catalyzed by D622G was higher than that by rAgaZC-1. The models of D622G and rAgaZC-1 predicted by homology modeling were compared to find that it is the improved distribution of surface electrostatic potential, great symmetric positive potential and more hydrophobic interactions of D622G that enhance the thermo-stability.
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