Thiol-dependent membrane-bound metallo-endopeptidase functioning in degradation of luteinizing hormone-releasing hormone in neuroblastoma cells and rat brain synaptic membrane. Isolation and characterization

Abstract

An endopeptidase generating fragment (1–5) from luteinizing hormone-releasing hormone (LHRH) has been solublized with Brij 35 from neuroblastoma cell membrane and purified by a procedure including p-mercuribenzoate-Sepharose chromatography, Mono-Q high-performance liquid chromatography and Superose 6 gel filtration. The molecular weight of the enzyme was estimated to be 100000 by gel filtration. LHRH fragment (1–5)-generating activity of the enzyme was strongly inhibited by metal-chelating and sulfhydryl-blocking reagents. An enzyme with similar properties to those of the neuroblastoma enzyme was also purified from rat brain synaptic membranes. The properties of the two purified enzymes corresponded to those of a thiol-dependent protease proposed to be the enzyme responsible for the initial cleavage of LHRH by neuroblastoma cell membranes and rat brain synaptic membranes.