AiM  Vol.5 No.7 , July 2015
Impact of Leucine 278 Residue on Fatty Acid Length Specificity of Candida antarctica Lipase B
ABSTRACT
Structural analysis of Candida antarctica lipase B (CALB) indicates that side chain of leucine at 278 site lies above the entrance of the catalytic pocket, which prognosticates its potential role on substrate specificity of the enzyme. To verify this presumption, shortened side chain of glycine or proline was rational designed and mutants were constructed by site-directed mutagenesis method. The colorimetric assay using p-nitrophenyl esters of fatty acids with various chain-lengths was used to study the substrate preference of lipases. Results indicated that L278G or L278P mutations both induced the drift of substrate specificity of CALB from p-nitrophenyl caprylate (pNP-C8) to longer carbon chain length of p-nitrophenyl caprate (pNP-C10). Meanwhile, Vmax value of two mutants to pNP-C10 was both higher than that of wild-type. Docking results also indicated that shortened side chain of glycine or proline residues substitution at this site could get rid of the space block present above the catalytic pocket, and made longer chain substrate (pNP-C10) enter into the catalytic pocket easier. The modulation of specificity observed allowed for building substrate binding model and opened new possibilities for designing ligand specific lipases.

Cite this paper
Wang, F. , Hou, S. , Wang, Q. , Wang, P. , Liu, J. , Yang, B. and Wang, Y. (2015) Impact of Leucine 278 Residue on Fatty Acid Length Specificity of Candida antarctica Lipase B. Advances in Microbiology, 5, 493-499. doi: 10.4236/aim.2015.57050.
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