Immobilization of maltase from Saccharomyces cerevisiae on thiosulfonate supports

Abstract

In this study, two commercial supports (Eupergit (R) C and Purolite (R) A109) were chemically modified in order to introduce thiosulfonate groups, which could subsequently exclusively react with the cysteine residues on the surface of enzymes. Thereafter, the maltase from Saccharomyces cerevisiae was immobilized onto the obtained thiosulfonate-activated supports, resulting in high expressed enzymatic activities (around 50 %), while on the other hand, immobilization on unmodified supports yielded expressed activities less than 5 %. Moreover, protein loadings up to 12.3 mg g(-1) and immobilized activities up to 3580 IU g(-1) were achieved by employment of these thiosulfonate supports. Desorption experiments, performed on samples taken during immobilization, proved that immobilization on the thiosulfonate supports was the first step of fast adsorption onto the supports and the formation of covalent bonds between the thiosulfonate groups and the thiol groups of cysteine represented a second slower step. More importantly, although enzyme coupling occurred via covalent bond formation, the performed immobilization proved to be reversible, since it was shown that 95 % of the immobilized activity could be detached from the support after treatment with a thiol reagent (beta-mercaptoethanol). Thus, the support could be reused after enzyme inactivation.