The enzymatic hydrolysis of a synthetic biomembrane: a new substrate for cholesterol and carboxyl esterases.

Abstract

With the introduction of artificial implant devices, a new host of biomembrane-like structures have been introduced into the bio-media made up of the synthetic matrix, adsorbed proteins and lipids. Lysosomal hydrolases, e.g. cholesterol esterase (CE), are implicated during the tissue response near the tissue-implant interface. The enzymatic attack on a radiolabelled 'hybrid biomembrane', a polyester-urethane (PUU-CAP), was investigated using two esterases. Membrane stability was monitored by release of radiolabelled molecules. Although some radioactivity was released by buffer controls, upon the addition of CE, a burst of radiolabel release occurred which was due to an enzymatic reaction that could be saturated and inhibited by the specific esterase inhibitor, phenylmethylsulfonylfluoride. Carboxyl esterase (CXE) incubation with PUU-CAP caused less radiolabel release than CE which was similar to the latter's activity when common nitrophenyl ester substrates were used. When a factorial analysis was performed, it was found that side chain length for the common substrates was twice more important for CE, than CXE activity. This would suggest that CE activity is greater for substrates which have spacer segments between potential ester-carbonyl cleavage sites and the rigid ring structure.