A study on the functional subunits of phospholipases A2 by enzyme immobilization

Efficient heterologous expression in Pichia pastoris, immobilization and functional characterization of a scorpion venom secreted phospholipase A2

Industrial processes have expanded with the ability to clone and express recombinant immobilized enzymes in microorganisms such as Pichia pastoris that have commercially attractive amounts of the appropriate genes. This report describes the overexpression in Pichia pastoris, immobilization, and functional characterization of a secreted phospholipase A₂ from scorpion venom Scorpio maurus: rPLA₂(-5). After 48 h of culture, the recombinant rPLA₂(-5) was secreted into the culture medium and expressed at about 9 mg/L. Comparative analyses of the kinetics and hydrolysis of rPLA₂(-5) monolayers at various surface pressures were conducted with the same form produced in Escherichia coli. As a second part of the study, rPLA₂(-5) overexpressed in Pichia pastoris was immobilized by adsorption on CaCO₃, with about 78 percent of the activity. In comparison to the free enzyme, rPLA₂(-5) was studied for stability. Immobilization improved the thermal stability of rPLA₂(-5) and even the stability at acidic pH. Moreover, we found that the immobilization improved the stability of rPLA₂(-5) towards bile salts, Tween 80, Triton X-100, and SDS, as well as its stability towards many organic solvents. Until now, this is the first study to describe the overexpression and immobilization of a scorpion venom phospholipase A₂ that possesses an interesting stability characteristic that makes it useful for a wide range of biotechnological applications.

A method of immobilization on the solid support of complex and simple enzymes retaining their activity

Immobilization of native proteins, retaining their activity, on the solid support is often crucial for a variety of biochemical assays involving protein-protein interactions. In this study we describe a technique which allows binding of both complex (protein kinase CK2) and simple (calf intestine alkaline phosphatase, CIP) enzymes to the solid support without denaturization of the proteins. This method is based on the covalent cross-linking of the enzymes to the bifunctional resin, containing the secondary amino and thiol groups, in a coupling reaction with the imidoester dimethyl pimelimidate hydrochloride. Both enzymes in their bound form were active in the specific biochemical assays. We also found that the CK2 and CIP resins did not change their activity for at least 3 months, and the quality of these resins were not affected by high salts or reducing agents. Thus, this method can be recommended for general use to generate active enzymes coupled to the solid support.