Enkephalin Dipeptidyl Carboxypeptidase (Enkephalinase) Activity: Selective Radioassay, Properties, and Regional Distribution in Human Brain
Enkephalin Dipeptidyl Carboxypeptidase (Enkephalinase) Activity: Selective Radioassay, Properties, and Regional Distribution in Human Brain
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脑啡肽二肽基羧肽酶（脑啡肽酶）活性：人脑中的选择性放射测定、特性和区域分布
作者：
C. Llorens;Bernard Malfroy;J. Schwartz;G. Gacel;B. Roques;J. Roy;Morgat Jl;F. Javoy‐Agid;Yves Agid
摘要：化合物[3 H-Tyr 1，D-Ala 2，Lcu-OH 5]脑啡肽已被合成为脑啡肽二肽基羧肽酶（脑啡肽酶）活性的潜在选择性底物。在存在啮齿动物和人脑匀浆和微粒组分的情况下进行孵育，导致形成[3 H] Tyr-D-Ala-Gly，其可通过聚苯乙烯珠柱色谱法方便地分离。负责水解该底物的Gly 3-Phe 4酰胺键的酶活性显示出与水解相同水平的天然脑啡肽的酶活性非常相似。此外，脑啡肽酶活性的特点是在死后的人的大脑是非常相似的啮齿动物的大脑，在最佳pH值和表观亲和力的各种底物和抑制剂，包括有效的化合物thiorphan。脑啡肽酶活性在人脑各区域之间以高度不均匀的方式分布，在苍白球和黑质网状部发现最高水平。这种分布与阿片受体结合位点的相关性较差，但与报告的Met 5-脑啡肽水平显示出一些相似性。
Abstract: The compound [3H‐Tyr1,D‐Ala2,Lcu‐OH5]enkephalin has been synthesised as a potentially selective substrate for enkephalin dipeptidyl carboxypcptidase (enkephalinase) activity in brain. lncubations in the presence of homogenates and particulate fractions from rodent and human brain result in the formation of [3H]Tyr‐D‐Ala‐Gly, which can be conveniently isolated by polystyrene bead column chromatography. The enzyme activity responsible for the hydrolysis of the Gly3‐Phe4 amide bond of this substrate displays close resemblance to that hydrolysing the natural enkephalins at the same level. In addition, enkephalinase activity characterised in postmortem human brain is closely similar to that in rodent brain, with regard to optimal pH and apparent affinities of various substrates and inhibitors, including the potent compound thiorphan. Enkephalinase activity is distributed in a highly heterogeneous fashion among regions of human brain, the highest levels being found in globus pallidus and pars reticulata of the substantia nigra. This distribution is poorly correlated with that of opiate receptor binding sites but displays some resemblance to that of reported Met5‐enkephalin levels.