Orawski A T, Simmons W H
Department of Molecular and Cellular Biochemistry, Loyola University of Chicago Stritch School of Medicine, Maywood, IL 60153.
Neurochem Res. 1992 Aug;17(8):817-20. doi: 10.1007/BF00969018.
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.
神经肽京都啡肽（酪氨酸 - 精氨酸）可被大鼠脑突触体通过一种与突触膜结合的肽酶降解，该肽酶可被贝司他汀抑制，但不能被抑氨肽酶抑制。京都啡肽的米氏常数（Km）为8×10^(-6) M，贝司他汀的抑制常数（Ki）为1×10^(-7) M。京都啡肽降解酶与突触体中至少一种其他二肽水解活性不同，后者可被贝司他汀和抑氨肽酶同时抑制。用去污剂提取突触体后进行凝胶渗透色谱，可分离出二肽水解活性。观察到一个单一的京都啡肽降解酶峰，其相对分子质量（M(r)）为52,000。该活性峰可降解其他二肽，包括苯丙氨酸 - 精氨酸，后者是缓激肽的一种突触膜生成的代谢产物。京都啡肽降解酶似乎是一种新的酶，可根据底物特异性、亚细胞定位和抑制谱与其他已知的二肽酶区分开来。
