Proteolytic processing of farnesylated peptides: assay and partial purification from pig brain membranes of an endopeptidase which has the characteristics of E.C. 3.4.24.15.

The proteolytic processing of farnesylated peptides was investigated with the tritiated C-terminal heptapeptide of mouse N-Ras protein, Propionyl-Gly-Ser-Pro-(farnesyl-Cys)-[3H]Val-Leu-Met, as substrate. Using two rapid and sensitive methods, the peptidase which cleaves the (farnesyl-Cys)-[3H]Val bond was purified more than 100 times from a microsomal fraction of pig brain. The determination of its molecular mass (about 70 kDa) and its pH range for optimum activity (neutral pH) as well as the results obtained with various inhibitors indicate that this [3H]Val-Leu-Met releasing enzyme resembles endopeptidase 24.15: a thiol-dependent zinc metallopeptidase. Parallel and comparative inhibition assays on partially purified enzyme and pure "24.15" confirm this similarity.