Dipeptidase activities in rat brain synaptosomes can be distinguished on the basis of inhibition by bestatin and amastatin: identification of a kyotorphin (Tyr-Arg)-degrading enzyme.
The neuropeptide kyotorphin (Tyr-Arg) was degraded by rat brain synaptosomes via a synaptic membrane-bound peptidase which was inhibited by bestatin but not by amastatin. The Km for kyotorphin was 8 x 10(-6) M and the Ki for bestatin was 1 x 10(-7) M. The kyotorphin-degrading enzyme was distinguished from at least one other dipeptide-hydrolyzing activity in synaptosomes which was inhibited by both bestatin and amastatin. Gel permeation chromatography of detergent-extracted synaptosomes resulted in the separation of the dipeptide-hydrolyzing activities. A single kyotorphin-degrading enzyme peak was observed which had a M(r) = 52,000. The activity peak could degrade other dipeptides including Phe-Arg, a synaptic membrane-generated metabolic of bradykinin. The kyotorphin-degrading enzyme appears to be novel and can be distinguished from other known dipeptidases on the basis of substrate specificity, subcellular localization, and inhibition profile.
Orawski
A T
AT
Department of Molecular and Cellular Biochemistry, Loyola University of Chicago Stritch School of Medicine, Maywood, IL 60153.
Simmons
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WH
D000818:Animals; D000900:Anti-Bacterial Agents; D001921:Brain / Q000201:enzymology*; D002850:Chromatography, Gel; D003902:Detergents; D004150:Dipeptidases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004723:Endorphins / Q000378:metabolism*; D007930:Leucine / Q000031:analogs & derivatives* / Q000494:pharmacology; D009842:Oligopeptides / Q000494:pharmacology; D010455:Peptides; D051381:Rats; D011919:Rats, Inbred Strains; D013379:Substrate Specificity; D013574:Synaptosomes / Q000201:enzymology*
D000900:Anti-Bacterial Agents; D003902:Detergents; D004723:Endorphins; D009842:Oligopeptides; D010455:Peptides; C019448:kyotorphin; C016977:amastatin; D004150:Dipeptidases; D007930:Leucine; C012211:ubenimex