Influence of water activity and support material on the enzymatic synthesis of a CCK-8 tripeptide fragment

The kinetically controlled condensation of Z-Gly-Trp-OMe and H-Met-OEt catalyzed by cr-chymotrypsin in organic media is reported. The influence of thermodynamic water activity and the support material used to adsorb ol-chymotrypsin, on both the product yield and enzymatic activity was investigated. Polyamide based materials were the best support at low water activity rendering the highest reaction rates and yields. The activity of the adsorbed enzyme at low water activities depends on both the accessible surface area and the hydrophobicity of the support. Polyamide had both adequate hydrophilicity and high surface area yielding the best results. Polypropylene based supports were strongly hydrophobic and, although they presented a high surface area, the enzymatic activity was much lower. The solvents used to carry out the synthesis were acetonitrile and ethyl acetate. No significant differences were observed on the performance of the reaction in either solvent. The tripeptide selected is a fragment of the cholecystokinin C-terminal octapeptide (CCK-8), a biological active peptide involved in the control of gastrointestinal function.