REMODELED ENZYME .2. ENZYMATIC FUNCTIONS OF FATTY ACID-MODIFIED CHYMOTRYPSIN AND TRYPSIN IN AQUEOUS-ORGANIC MEDIA

In our previous paper we demonstrated that chemical modification using the water-soluble acylating reagent, [p-hydroxy]phenyldimethylsulfoni um methylsulfate, enabled us to introduce a variety of hydrophobic mod ifying groups into an enzyme molecule in an aqueous medium under mild conditions. To investigate the effects of these introducing groups on the hydrolytic activity of the modified enzyme, chymotrypsin and tryps in were modified with acetyl, decanoyl, lauroyl, myristoyl, and palmit oyl groups. We found an optimum carbon chain length and an optimum mod ification ratio for the fatty acid-modified enzyme to catalyze a hydro lytic reaction in aqueous-organic media, and the correlation between t he hydrolytic activity and the dispersibility in the aqueous-organic m edia. Compared with the unmodified enzyme, the chemical modification r educed K(m), but had no significant effect on k(cat). The chemical mod ification seems to promote the dispersibility of the enzymes in aqueou s-organic media, and leads to increasing the affinity of the enzyme to a substrate.