ENZYMATIC DEGRADATION OF POLY[N-5-(2-HYDROXYETHYL)-L-GLUTAMINE] AND Y[N-5-(2-HYDROXYETHYL)-L-GLUTAMINE-STAT-L-GLUTAMIC ACID] - ANALYSIS OF FINAL DEGRADATION PRODUCTS

The enzymatic degradation of N-5-(2-hydroxyethyl)-L-glutamine homopoly mer (PHEG) and its statistical copolymer with L-glutamic acid, (P[HEG- stat-Glu]) by papain, pronase and leucine aminopeptidase (LAP) was inv estigated with the aim to evaluate the role of endopeptidase and exope ptidase mechanisms of cleavage and to identify ultimate degradation pr oducts. The degradation products were analysed by size-exclusion chrom atography, using amino end-groups labelled with fluorescamine, and by thin-layer chromatography. Papain cleaved both polymers by the endopep tidase mechanism only and the smallest degradation fragments thus prod uced were the size of tetramers. These fragments were susceptible to f urther degradation by an exopeptidase, i.e., leucine aminopeptidase. A combined treatment of polymers by papain and LAP ultimately yielded m onomers, HEG only or HEG and glutamic acid for PHEG or P[HEG-stat-Glu] copolymer, respectively. Both endopeptidase and exopeptidase mechanis ms were active in the degradation of the polymers under study by prona se. As the enzymes with analogous specificities are usually present in mammalian tissues, the feasibility of complete degradation of these p olymers in vivo is supported.