Activity Enhancement of Candida antarctica Lipase B by Flexibility Modulation in Helix Region Surrounding the Active Site

The activity of Candida antarctica lipase B was improved by mutation of the area surrounding the active site. We changed the edges of four helices surrounding the active site to flexible amino acids. Two mutants, V139E and I255E, obtained as a result of Pichia pastoris expression, showed enhanced specific activity of 9.9 and 8.1 U/mg while that of wild type was 2.3 U/mg for p-nitrophenyl caprylate hydrolysis. It was nearly 5.4-fold and 3.5-fold, respectively. The stability of both mutants on organic solvent was slightly decreased but almost similar with that of wild type. In the kinetic assay, k (cat) values were shown as dominant factor for the enhancement of catalytic efficiency, k (cat)/K (m), since it was 4.1-fold and 3.8-fold, respectively.