Hook V Y
Neuropeptides. 1984 Mar;4(2):117-26. doi: 10.1016/0143-4179(84)90122-7.
Trypsin and carboxypeptidase B-like (CPB-like) peptidases should be involved in processing proenkephalin to form the small biologically active enkephalins. A carboxypeptidase B-like activity from the soluble fraction of bovine adrenomedullary chromaffin granules which converts 125I-(Met)-enkephalin-Arg6 to 125I-(Met)enkephalin has previously been described and characterized (1,2). In this study, CPB-like activity in the membrane bound component of chromaffin granules is characterized and compared with that in the soluble fraction. Membrane and soluble CPB activities cleaved 125I-(Met)enkephalin-Arg6 or 125I-(Met)enkephalin-Lys6 to form 125I-(Met)enkephalin. Like the soluble enzyme, the CPB-like activity in the membrane component had a pH optimum of 6.0, was inhibited by thiol agents (PCMPSA, CuCl2) and metal ion chelators (EDTA, 1,10-phenanthroline), and was stimulated by Co++. The membrane CPB-like activity appeared to be an intrinsic membrane protein, since 80% of the activity remained with the membranes after washing with 1.0 M NaCl. Membrane and soluble CPB-like activities in chromaffin granules appear to be similar enzymes.
胰蛋白酶和类羧肽酶B（CPB样）肽酶应参与前脑啡肽的加工过程，以形成具有生物活性的小的脑啡肽。先前已描述并表征了来自牛肾上腺髓质嗜铬颗粒可溶部分的一种类羧肽酶B活性，该活性可将125I-（蛋氨酸）-脑啡肽-精氨酸6转化为125I-（蛋氨酸）脑啡肽（1,2）。在本研究中，对嗜铬颗粒膜结合成分中的CPB样活性进行了表征，并与可溶部分中的活性进行了比较。膜和可溶部分的CPB活性均可切割125I-（蛋氨酸）-脑啡肽-精氨酸6或125I-（蛋氨酸）-脑啡肽-赖氨酸6，以形成125I-（蛋氨酸）脑啡肽。与可溶酶一样，膜成分中的CPB样活性在pH 6.0时最适宜，受硫醇试剂（对氯汞苯磺酸钠、氯化铜）和金属离子螯合剂（乙二胺四乙酸、1,10-菲咯啉）抑制，并受钴离子刺激。膜CPB样活性似乎是一种内在膜蛋白，因为用1.0 M氯化钠洗涤后，80%的活性仍保留在膜上。嗜铬颗粒中的膜和可溶CPB样活性似乎是相似的酶。
