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 influe nce of thermodynamic water activity and the support material used to a dsorb ol-chymotrypsin, on both the product yield and enzymatic activit y was investigated. Polyamide based materials were the best support at low water activity rendering the highest reaction rates and yields. T he 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 yie lding the best results. Polypropylene based supports were strongly hyd rophobic and, although they presented a high surface area, the enzymat ic activity was much lower. The solvents used to carry out the synthes is were acetonitrile and ethyl acetate. No significant differences wer e observed on the performance of the reaction in either solvent. The t ripeptide selected is a fragment of the cholecystokinin C-terminal oct apeptide (CCK-8), a biological active peptide involved in the control of gastrointestinal function.