Abstract

The aim of this work was to study different immobilization strategies on silica supports in order to obtain robust biocatalysts from latex proteases of Asclepias curassavica L., a South American native plant. Immobilized enzyme performance was evaluated under harsh reaction conditions such as the synthesis of the antihypertensive peptide N-alpha-CBZ-Val-Gly-OH. Proteases from A. curassavica, named asclepain, were immobilized (0.51-5.56 mg of protein/ g of support) in non-functionalized silica (S), in glyoxyl-silica (GS) and in octyl-glyoxyl-silica (OGS), by adsorption, and multipoint covalent attachment on mono and hetero-functional supports, respectively, under previously determined optimal immobilization conditions. Immobilization yields were expressed as activity yield (Y-a) and protein yield (Y-p). Asclepain-OGS showed the highest Y-a (178 +/- 1.62 %) meaning an expressed activity 1.8 times higher than the offered activity, while Y-p was 75 +/- 0.4 %. Y-a for asclepain-S and -GS were 64 +/- 1.45 % and 16 +/- 0.37 %, respectively. Best results were attributed to the ability of OGS support to guide the enzyme before covalent attachment, increasing its reactivity. Asclepain-OGS led to product yield of 95.5 +/- 0.14 %, five times higher than soluble asclepain in the synthesis of N-alpha-CBZ-Val-Gly-OH, after 3 h in 30 % methanol in 0.1 M Tris-HCl buffer pH 8.