Directed evolution to enhance secretion efficiency and thermostability of chitosanase from Mitsuaria chitosanitabida 3001.
Chitosanase (ChoA) from Mitsuaria chitosanitabida 3001 was successfully evolved with secretion efficiency and thermal stability. The inactive ChoA mutant (G151D) gene was used to mutate by an error-prone PCR technique and mutant genes that restored chitosanase activity were isolated. Two desirable mutants, designated M5S and M7T, were isolated. Two amino acids, Leu74 and Val75, in the signal peptide of ChoA were changed to Gln and Ile respectively in the M7T mutant, in addition to the G151D mutation. The L74Q/V75I double ChoA mutant was 1.5-fold higher in specific activity than wild-type ChoA due to efficient secretion of ChoA. One amino acid Asn222 was changed to Ser in the M5S mutant in addition to the G151D mutation. The N222S single ChoA mutant was 1.2-fold higher in specific activity and showed a 17% increase in thermal stability at 50 degrees C as compared with wild-type ChoA. This is the first study to achieve an evolutional increase in enzyme capability among chitosanses.
Yun
Choongsoo
C
Department of Applied Bioscience and Biotechnology, Faculty of Life and Environmental Science, Shimane University, Japan.
Matsuda
Hideyuki
H
Kawamukai
Makoto
M
D019117:Burkholderia / Q000201:enzymology* / Q000235:genetics; D048271:Chitosan / Q000378:metabolism; D019020:Directed Molecular Evolution; D004795:Enzyme Stability; D006026:Glycoside Hydrolases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D013379:Substrate Specificity; D013696:Temperature
D048271:Chitosan; D006026:Glycoside Hydrolases; C019868:chitosanase