Alteration of substrate specificity of Galactomyces geotrichum BT107 lipase I on eicosapentaenoic acid-rich triglycerides

Abstract

One cycle of random mutagenesis and screening of an expression mutant library in P. pastoris was used to isolate two variants of Galactomyces geotrichum BT107 lipase I showing a 2-fold reduction in their hydrolytic activity towards the homogeneous triglyceride of eicosapentaenoic acid (triEPA, C20:5 n-3) compared with the wild-type enzyme. Only one amino acid substitution on each variant was enough to decrease their activity on this polyunsaturated substrate. The activity of the enzyme for triglycerides containing oleic acid was scarcely affected. Results obtained after hydrolysis of commercial marine oil confirmed the low lipolytic activity of one of the variants toward glycerides containing EPA. The amino acid substitutions were located in the lid region pointing out the role of this structure on substrate selectivity. This is a good starting point to obtain enzyme variants than can be used to enrich oils in PUFAs fraction, mainly EPA, from fish oils.

• Galactomyces geotrichum
• lipase I
• eicosapentaenoic acid
• PUFAS
• Pichia pastoris