Lonovics J, Penke B, Rayford P L, Thompson J C
Hepatogastroenterology. 1986 Feb;33(1):27-33.
We have studied the capacity of different canine tissue homogenates to destroy cholecystokinin in vitro. Tissues from the kidney cortex, lung, pancreas, and small bowel contained significant cholecystokinin-destroying activity. Only small amounts of activity were found in the liver, and no activity was detected in the kidney medulla, the gastric antrum, gallbladder, spleen, or in serum or plasma. The kidney cortex was the richest source of activity. The cholecystokinin-destroying enzyme isolated from the kidney cortex was heat-labile, non-dialyzable, and trypsin-resistant, with an optimum pH between 7 and 7.4. The enzyme was inhibited by chelating agents and by phenylalanine amide, although it was little affected by phenylalanine itself or proteinase inhibitors. The enzyme required divalent cation cofactors for its activity. After inhibition by EDTA, the enzyme could be reactivated completely with Mn2+, but not with Ca2+ or Mg2+ alone. The cholecystokinin-destroying enzyme was bound strongly to membranes, and during differental centrifugation, was sedimented with mitochondrial fractions of kidney cortex. The supernatant fraction of the solubilized enzyme obtained at 105,000 X g had a molecular weight of about 480,000 dalton. Since the enzyme could be inhibited by phenylalanine-amide, it would appear to act at the C-terminal end of the cholecystokinin molecule.
我们已经研究了不同犬类组织匀浆在体外破坏胆囊收缩素的能力。肾皮质、肺、胰腺和小肠组织含有显著的胆囊收缩素破坏活性。在肝脏中仅发现少量活性，而在肾髓质、胃窦、胆囊、脾脏、血清或血浆中未检测到活性。肾皮质是活性最丰富的来源。从肾皮质分离出的胆囊收缩素破坏酶对热不稳定、不可透析且对胰蛋白酶有抗性，最适pH在7至7.4之间。该酶受到螯合剂和苯丙氨酸酰胺的抑制，尽管它受苯丙氨酸本身或蛋白酶抑制剂的影响较小。该酶的活性需要二价阳离子辅助因子。被EDTA抑制后，该酶可被Mn2+完全重新激活，但不能仅被Ca2+或Mg2+重新激活。胆囊收缩素破坏酶与膜紧密结合，在差速离心过程中，与肾皮质的线粒体部分一起沉淀。在105,000×g下获得的溶解酶的上清部分的分子量约为480,000道尔顿。由于该酶可被苯丙氨酸酰胺抑制，它似乎作用于胆囊收缩素分子的C末端。
