Functional properties and application in peptide synthesis of trypsin modified with cyclodextrin-containing dicarboxylic acids

Bovine pancreatic trypsin was chemically modified with several β-cyclodextrin (CD) derivatives containing adipic, pimelic and dodecanodioic acids using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDAC) as coupling agent. The modifying agents used were mono-6-(4-carboxybutane-1-carboxamidoyl)-6-deoxy-β-cyclodextrin, mono-6-(5-carboxypentane-1-carboxamidoyl)-6-deoxy-β-cyclodextrin and mono-6-(10-carboxydecane-1-carboxamidoyl)-β-cyclodextrin. The modified enzymes contained about 6 mol of oligosaccharide per mol of trypsin. The catalytic and stability properties of trypsin were improved after the chemical modification. The thermostability profile of CD-modified trypsins was increased by about 10–14 °C. The conjugates were also more stable against thermal incubation at different temperatures ranging from 45 to 60 °C. In comparison with native trypsin, the cyclodextrin–enzyme conjugates were markedly more resistant to autolytic degradation at pH 9.0. Furthermore, the CD–trypsin conjugates gave higher aminolysis rates in kinetically controlled peptide synthesis reactions. The results reported here suggest that conjugation of enzymes with β-cyclodextrin derivatives is a useful method for improving the stability and the catalytic properties of these biocatalysts.