Reductive alkylation of lipase: experimental and molecular modeling approaches.
Candida rugosa lipase was modified via reductive alkylation to increase its hydrophobicity to work better in organic solvents. The free amino group of lysines was alkylated using propionaldehyde with different degrees of modification obtained (49 and 86%). Far-ultraviolet circular dichroism (CD) spectroscopy of the lipase in aqueous solvent showed that such chemical modifications at the enzyme surface caused a loss in secondary and tertiary structure that is attributed to the enzyme unfolding. Using molecular modeling, we propose that in an aqueous environment the loss in protein structure of the modified lipase is owing to disruption of stabilizing salt bridges, particularly of surface lysines. Indeed, molecular modeling and simulation of a salt bridge formed by Lys-75 to Asp-79, in a nonpolar environment, suggests the adoption of a more flexible alkylated lysine that may explain higher lipase activity in organic solvents on alkylation.
Enzyme and Microbial Technology Research, Faculty of Science and Environmental Studies, Institute of Bioscience, Universiti Putra Malaysia, 43400 Serdang. rnzaliha@fsas.upm.edu.my
Raja Noor Zaliha A
RN
Rahman
Bimo Ario
BA
Tejo
Mahiran
M
Basri
Mohd Basyaruddin A
MB
Rahman
Farid
F
Khan
Sharifuddin M
SM
Zain
Teruna J
TJ
Siahaan
Abu Bakar
AB
Salleh
D000478:Alkylation; D002175:Candida / Q000201:enzymology; D002942:Circular Dichroism; D006860:Hydrogen Bonding; D008049:Lipase / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D008958:Models, Molecular; D010084:Oxidation-Reduction; D014166:Transferases / Q000378:metabolism*
D014166:Transferases; D008049:Lipase