Rodd D, Hersh L B
Department of Biochemistry, University of Kentucky, Lexington 40536-0084, USA.
J Biol Chem. 1995 Apr 28;270(17):10056-61. doi: 10.1074/jbc.270.17.10056.
A peptidase, isolated from rat testes, is inhibited by 1 mM o-phenanthroline, 1 microM N-(1-(R,S)-carboxyl-3-phenylpropyl)-Ala-Ala-Phe-p-aminobenzoate, and 6 mM Pro-Ile, properties similar to those ascribed to endopeptidase 24.16. The enzyme hydrolyzes dynorphin A-8, neurotensin 1-13, angiotensin I, and substance P. Kinetic analysis of a series of angiotensin I analogs showed that substitutions at P-1, P-1', or P-2' had little effect on Km or Kcat. Variation of peptide size with a series of dynorphin A peptides showed chain length to be significant. The peptidase cleaved dynorphin A-8 at both Leu5-Arg6 and Arg6-Arg7, and neurotensin 1-13 at Pro10-Tyr11 and Arg8-Arg9. In contrast, rat endopeptidase 24.16 cleaves dynorphin A-8 at Gly4-Leu5 and Leu5-Arg6, and neurotensin 1-13 only at Pro10-Tyr11. These findings, as well as the observation that endopeptidase 24.16 exhibits a considerably higher affinity for Pro-Ile, Ki = 90 microM, indicates the peptidase isolated in this study is related to, but distinct from, rat endopeptidase 24.16. We propose that this new endopeptidase be referred to as endopeptidase 24.16B, while the originally described enzyme be referred to as endopeptidase 24.16A.
从大鼠睾丸中分离出的一种肽酶，可被1 mM邻菲罗啉、1 μM N-(1-(R,S)-羧基-3-苯基丙基)-丙氨酰-丙氨酰-苯丙氨酰-对氨基苯甲酸和6 mM脯氨酰-异亮氨酸抑制，其特性与内肽酶24.16相似。该酶可水解强啡肽A-8、神经降压素1-13、血管紧张素I和P物质。对一系列血管紧张素I类似物的动力学分析表明，P-1、P-1'或P-2'处的取代对Km或Kcat影响很小。用一系列强啡肽A肽改变肽大小表明链长很重要。该肽酶在亮氨酸5-精氨酸6和精氨酸6-精氨酸7处切割强啡肽A-8，在脯氨酸10-酪氨酸11和精氨酸8-精氨酸9处切割神经降压素1-13。相比之下，大鼠内肽酶24.16在甘氨酸4-亮氨酸5和亮氨酸5-精氨酸6处切割强啡肽A-8，而在神经降压素1-13上仅在脯氨酸10-酪氨酸11处切割。这些发现，以及内肽酶24.16对脯氨酰-异亮氨酸表现出相当高亲和力（Ki = 90 μM）这一观察结果，表明本研究中分离出的肽酶与大鼠内肽酶24.16相关，但又有所不同。我们建议将这种新的内肽酶称为内肽酶24.16B，而最初描述的酶称为内肽酶24.16A。
