Effects of enzymes and protein modifying reagents on the binding of 3H-prostaglandin E2 to porcine oxyntic mucosa in vitro.

In the present study we have investigated the macromolecular nature of porcine oxyntic mucosal PGE2 binding sites and the involvement of specific functional groups in the binding interaction. Incubation of oxyntic mucosal membranes with DNAse or RNAse did not influence binding. Phospholipase A2 was strongly inhibitory while phospholipases C and D exerted variable effects. Trypsinization of the membranes also reduced binding and this reduction was prevented by addition of soybean trypsin inhibitor. Neuraminidase and beta-galactosidase treatments resulted in variable increases in binding activity. The increase in binding was due to an increase in binding affinity and/or binding site concentration. Protein modifying reagents acetic anhydride, N-ethylmaleimide and mercaptoethanol all reduced binding. These results suggest the importance of protein, lipid and carbohydrate components of the membrane in the binding interaction between PGE2 and its binding site. The ability of mercaptoethanol and N-ethylmaleimide to reduce binding suggest the involvement of both sulphydryl and disulphide groups in the PGE2 binding reaction.