engleski

Human dipeptidyl peptidase III acts like a postproline-cleaving enzyme on endomorphins

Due to its specific conformation, the amino acid proline imposes many structural restrictions on peptides and proteins, and also restricts the attack by most proteolytic enzymes. Especially sequences with proline in the N- or C-terminal penultimate position were considered to be resistant to non-specialised peptidases. The dipeptidyl peptidase III (DPP III) is a broad specificity zinc-exopeptidase, with a role indicated in mammalian pain-modulatory system, owing to its high affinity for enkephalins and localization in the superficial laminae of the spinal cord dorsal horn. Our study revealed that this human enzyme hydrolyses opioid peptides belonging to the three new groups, endomorphins, hemorphins and exorphins. The enzymatic hydrolysis products of endomorphin-1 were separated and quantified by capillary electrophoresis and kinetic parameters determined for human DPP III and rat DPP IV. Both peptidases cleaved endomorphin-1 with comparable rate, by liberating the N-terminal Tyr-Pro. This is the first evidence on DPP III acting as a postproline-cleaving exopeptidase.

aminopeptidase; capillary electrophoresis; hydrolase; opioid peptides

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