Improved functional properties of trypsin modified by monosubstituted amino-β-cyclodextrins

Bovine pancreatic trypsin was chemically modified by several beta-cyclodextrin (beta-CD) derivatives using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide as coupling agent. The modifying agents used were mono-6-amino-6-deoxy-beta-cyclodextrin (CDNH2), mono-6-ediylenediamino-6-deoxy-beta-cyclodextrin (CDEN), mono-6-propylenediamino-6-deoxy-beta-cyclodextrin (CDPN) and mono-6-butylenediamino-6-deoxy-beta-cyclodextrin (CDBN). The enzyme-cyclodextrin conjugates contained about 2 mol of oligosaccharide per mol of trypsin. The catalytic and thermal stability properties of trypsin were improved by the attachment of cyclodextrin residues, and these effects were markedly noticeable for cyclodextrin (CD) derivatives having an even number of carbon atoms in the spacer arms. The thermostability of the enzyme was increased by about 2.4-14.5 degreesC after modification. The conjugates prepared were also more stable against thermal incubation at different temperatures ranging from 45 to 60degreesC. In comparison with native trypsin, the enzyme-cyclodextrin complexes were markedly more resistant to autolytic degradation at pH 9.0. Attending to the results here reported, we suggest that conjugation of enzymes with beta-CD derivatives might be an useful method for improving the stability and the catalytic properties of these biocatalysts. (C) 2003 Elsevier Science B.V. All rights reserved.