Synthesis and catalytic activity of poly-L-histidyl-L-aspartyl-L-seryl-glycine

Poly(His-Asp-Ser-Gly) was synthesized from the fully protected tetrapeptide active ester hydrochloride, which was prepared by stepwise coupling, using pentachlorophenyl ester and mixed anhydride methods. Complete deprotection of the protected tetrapeptide polymer was achieved by using 90% trifluoroacetic acid. The free polymer was dialyzed for 24 hr using a membrane (which retains molecules with molecular weights greater than 5000). The catalytic activity was determined by studying the hydrolysis of p-nitrophenyl acetate in 0.2 M phosphate buffer (pH 7.4) at 37 degrees. The catalytic coefficient of the dialyzed polymer was found to be 138 liters/mole/min.