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 |
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Authors: | Arthur T. Orawski William H. Simmons Ph.D. |
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Affiliation: | (1) Department of Molecular and Cellular Biochemistry, Loyola University of Chicago Stritch School of Medicine, 2160 S. First Avenue, 60153 Maywood, IL |
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Abstract: | 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 8×10–6 M and the Ki for bestatin was 1×10–7 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 detergentextracted synaptosomes resulted in the separation of the dipeptide-hydrolyzing activities. A single kyotorphin-degrading enzyme peak was observed which had a Mr=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. |
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Keywords: | Kyotorphin dipeptidase metabolism amastatin bestatin rat brain |
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