Matsas, Rebecca;
Turner, Anthony J.;
Kenny, A.John
Endopeptidase‐24.11 and aminopeptidase activity in brain synaptic membranes are jointly responsible for the hydrolysis of cholecystokinin octapeptide (CCK‐8)
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Media type:
E-Article
Title:
Endopeptidase‐24.11 and aminopeptidase activity in brain synaptic membranes are jointly responsible for the hydrolysis of cholecystokinin octapeptide (CCK‐8)
Contributor:
Matsas, Rebecca;
Turner, Anthony J.;
Kenny, A.John
Description:
<jats:p>Endopeptidase‐24.11 (EC 3.4.24.11) from pig kidney hydrolysed CCK‐8 (sulphated) at two distinct sites: Asp‐Tyr(SO<jats:sub>3</jats:sub>H)‐Met‐Gly↓Trp‐Met‐Asp↓PheNH<jats:sub>2</jats:sub>. Under initial conditions, the splitting of the Asp<jats:sup>7</jats:sup>‐Phe<jats:sup>8</jats:sup>NH<jats:sub>2</jats:sub> bond proceeded 4‐times more rapidly than the Gly<jats:sup>4</jats:sup>‐Trp<jats:sup>5</jats:sup> bond. Pig brain striatal synaptic membranes attacked this substrate at the same sites and this activity was inhibited by phosphoramidon. However, other products were detected even in the presence of phosphoramidon. One of these products was identified as free tryptophan. Since their formation was inhibited by bestatin, one or more membrane aminopeptidases is also implicated in the degradation of CCK‐8.</jats:p>