Sequence‐based proline incorporation improves the thermostability of Candida albicans lipase Lip5

Abstract

Increasing kinetic stability of industrial enzymes is a key objective of protein engineering. In this study, a cold‐active Candida albicans lipase Lip5 was selected as a model to improve its stability. With no 3D structure available, multiple‐sequence alignment of homologous lipases with different kinetic stabilities in the same superfamily was used to identify the mostly likely positions relevant to protein stability; these positions (V39, I52, and I290) were selected for proline incorporation in Lip5 as a strategy to increase the protein stability. Of the mutants generated, two of them (V39P and I290P) displayed a twofold increase in kinetic stability and improved thermodynamic stability as well. None of the mutants exhibited secondary or tertiary structure changes as shown by circular dichroism and fluorescence spectroscopy analyses. These results demonstrate that in the absence of 3D structure, multiple‐sequence alignment could be a useful tool to direct proline incorporation for lipase stability engineering.Practical applications: In the absence of a 3D structure, multiple‐sequence alignment‐based proline incorporation is a useful tool to engineer lipase towards improved stability.The kinetic stability of Lip5 and mutants showed that t1/2 values of mutants V39P and I290P were approximately twice as high as that of the wild type. The ΔΔGs of these two mutants increased by 2.35 and 2.03 KJ/mol, respectively, compared with wild type, suggesting higher energy barriers against thermal inactivation for V39P and I290P. Proline incorporation at position 39 or 290 increases the kinetic stability of Lip5.