EFFECT OF ALKALI-HALIDES ON ALPHA-CHYMOTRYPSIN ACTIVITY IN THE PLASTEIN REACTION

The influence of different alkali halides (LiF, LiCl, LiBr, NaF, NaCl, NaBr, KF, KCl and KBr) on alpha-chymotrypsin-catalysed plastein synth esis has been studied in aqueous medium at different substrate concent rations. The results showed an enhancing effect on the plastein synthe sis enzyme action by the presence of salts, proportional to salt conce ntration, which was decreased when the substrate concentration was inc reased. Additionally, these facts allowed the ions to be classified as a function of their activation power (F- > Cl- > Br-; K+ > Na+ > Li+) , which was in agreement with the interpretation of the Hofmeister lyo tropic series. The influence of the several phenomena produced by the presence of salts in the plastein reaction, such as, salt-substrate in teractions and water activity, as well as the presence of deactivated enzyme was also analysed. The obtained results showed that the substra te concentration is the most important factor, and the activating effe ct of salts could be simultaneously involved with both a structural ch ange on the substrate conformation and a reduction of water activity i nto the reaction media, enhancing the catalytic capability of the alph a-chymotrypsin towards a peptide synthesis action.