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  • Title: Purification of and kinetic studies on a narrow specificity synaptosomal membrane pyroglutamate aminopeptidase from guinea-pig brain.
    Author: O'Connor B, O'Cuinn G.
    Journal: Eur J Biochem; 1985 Jul 01; 150(1):47-52. PubMed ID: 2862039.
    Abstract:
    A pyroglutamate aminopeptidase activity, distinct from that of cytoplasm, was released from a synaptosomal membrane preparation of guinea-pig brain by papain treatment. This activity was further purified 3560-fold relative to the homogenate with a yield of 17% by a procedure involving gel filtration chromatography, calcium phosphate cellulose chromatography and hydrophobic interaction chromatography on phenyl-Sepharose CL-4B. The purified synaptosomal pyroglutamate aminopeptidase hydrolysed only thyroliberin, acid-thyroliberin, the luliberin N-terminal tripeptide (Glp-His-Trp) and, only slightly, Glp-His-Gly. No hydrolysis was observed with dipeptides containing N-terminal pyroglutamic acid (Glp) or with pyroglutamyl peptides containing more than three amino acids. A Km value of 40 microM was recorded when thyroliberin was used as substrate; however, luliberin was found to inhibit the hydrolysis of thyroliberin competitively with a Ki value of 20 microM.
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