The effect of the typical peptidases (proteases) inhibitors on the degradation of Glp6 (125I) Tyr8SP6-11 hexapeptide in the nuclear and synaptosomal fraction of the cortex and hippocampus of rat brain.

The main peptidase PN/cutting Tyr8-Gly9 or Gly9-Leu10 bond (of sequence Glp6-Phe7-Tyr8-Gly9-Leu10-MetNH2) seems to be, at least in part, cysteine type enzyme. Cutting of Phe7-Tyr8 bond with PC enzyme is apparently negligible. Further degradation of labelled PN products seems to be accomplished with PI, being serine enzyme at least in part. Metalloenzymes, including "enkephalinase", seem to be of minor importance in hexapeptide degradation, at least in its very low concentration. Some typical inhibitors enhance the degradation what might be explained assuming that products of action of one peptidase strongly inhibit the other peptidase's action. Namely, products of PN and PI seem to inhibit PC except the hippocampal synaptosomes where the opposite is true.