N-α-acylation of lysine catalyzed by immobilized aminoacylases from Streptomyces ambofaciens in aqueous medium

Abstract

Aminoacylases (EC 3.5.1.1.4) of Streptomyces ambofaciens ATCC 23877 were immobilized by chemical and physical adsorption onto SBA-15 mesoporous silica materials. The activity of the immobilized aminoacylases was firstly evaluated by considering the hydrolysis reactions of N-α-acetyl-lysine, used as rapid method of screening. After chemical adsorption, a significant loss of activity was observed probably due to a conformational change of the aminoacylases structures upon immobilization. When the immobilization was performed by physisorption a higher amount of enzyme (0.20 against 0.05 mg per mg of support) can be adsorbed onto the mesoporous silica material. The physisorbed biocatalyst also presented a higher hydrolytic activity than the chemisorbed enzyme. Recycling of the supported biocatalysts was performed three times with no loss of the specific activity. Furthermore, a better thermostability was also noted in comparison with free enzyme upon aminoacylases physisorption.Finally, lauroyl-lysine synthesis was catalyzed for the first time by immobilized aminoacylases. The crude extract from S. ambofaciens exhibited the rare ability to catalyze the N-acylation on amino group in the α-position of the lysine whereas the lipase B of Candida antarctica catalyzed the acylation of lysine on its amino group in ε-position. This particular and original regioselectivity was maintained with immobilized enzymes.