Phenylboronic acid as a ligand for biospecific chromatography of serine proteinases

Via attachment of p-(omega-aminoethyl)phenylboronic acid to CH-Sepharose in the presence of water-soluble carbodiimide, a new sorbent for the biospecific chromatography of serine proteinases was obtained. The sorbent was shown to be suitable for the purification of subtilisn, alpha-chymotrypsin and trupsin. It is assumed that the serine hydroxyl group at the active site of the enzyme forms, with the boronic acid moiety of the ligand, a structure that imitates transition enzyme--substrage complex. The presence of glycerol selectively improves the binding of serine proteinases, presumably because of stabilization of the tetrahedral state of the boron atom. Direct isolation of subtilisin from a Bacillus subtilis cultural filtrate on phenylboronic acid-containing sorbent gives a virtually homogenous enzyme (42-fold purification) in a nearly-quantitative yield.