The degradation of somatostatin by synaptic membrane of rat hippocampus is initiated by endopeptidase-24.11.
Somatostatin was degraded by the synaptic membrane from rat hippocampus. Cleavage products were separated by reversed phase high performance liquid chromatography and identified by amino acid composition analyses and N-terminal amino acid and sequence determinations around the cleavage sites. Fragments produced from the cleavages at both or either sites between the Phe6-Phe7 and/or between the Thr10-Phe11, together with free phenylalanine and tryptophan, were major cleavage products, followed by that produced from the cleavage of the Asn5-Phe6 bond. The accumulation of the major cleavage products, as well as the initial cleavage of somatostatin, was strongly inhibited by metal chelators and also by specific inhibitors of endopeptidase-24.11 (EC 3.4.24.11), phosphoramidon and thiorphan. The inhibitor susceptibility of the synaptic membrane toward somatostatin was similar to that toward Leu-enkephalin, a natural substrate of endopeptidase-24.11. Furthermore, endopeptidase-24.11 purified from rat brain hydrolyzed somatostatin at the cleavage sites identical to those by the hippocampal synaptic membrane. Thus, it can be concluded that endopeptidase-24.11 plays a major role in the initial stage of somatostatin degradation in rat hippocampus.
Sakurada
C
C
Department of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
Yokosawa
H
H
Ishii
S
S
D000595:Amino Acid Sequence; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D004743:Enkephalin, Leucine / Q000378:metabolism; D006624:Hippocampus / Q000201:enzymology*; D006868:Hydrolysis; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D015260:Neprilysin / Q000302:isolation & purification / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism; D011480:Protease Inhibitors / Q000494:pharmacology; D051381:Rats; D013004:Somatostatin / Q000378:metabolism*; D013570:Synaptic Membranes / Q000201:enzymology*
D010446:Peptide Fragments; D011480:Protease Inhibitors; D013004:Somatostatin; D004743:Enkephalin, Leucine; D015260:Neprilysin