Han Y, Gao P, Yu W, Lu X. N-Terminal seven-amino-acid extension simultaneously improves the pH stability, optimal temperature, thermostability and catalytic efficiency of chitosanase CsnA.
Biotechnol Lett 2017;
40:75-82. [PMID:
28905142 DOI:
10.1007/s10529-017-2436-9]
[Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Accepted: 08/31/2017] [Indexed: 11/29/2022]
Abstract
OBJECTIVE
To determine the effects of the extra N-terminal seven-amino-acid sequence on the function of chitosanase CsnA.
RESULTS
Sequence and structure analysis indicated that the mature CsnA contains a seven-amino-acid extension in a disordered form at the N-terminus. To determine the function of this sequence, both mature CsnA and its N-terminus-truncated mutant, CsnAΔN, were expressed in Escherichia coli and characterized. Compared with CsnAΔN, CsnA exhibited a 15 °C higher temperature optimum, enhanced pH stability, thermostability and catalytic efficiency. The underlying mechanisms responsible for these changes were analyzed by circular dichroism (CD) spectroscopy. CD analysis revealed that the deletion of the N-terminal sequence resulted in a decrease in the Tm of 4.3 °C and this sequence altered the secondary structure of the enzyme.
CONCLUSIONS
The N-terminal sequence is essential for the stability and activity of chitosanase CsnA.
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