Aoyagi T, Suda H, Nagai M, Ogawa K, Suzuki J
Biochim Biophys Acta. 1976 Nov 8;452(1):131-43. doi: 10.1016/0005-2744(76)90064-4.
Activities of hydrolytic enzymes on the surface of monkey kidney, canine kidney, L. FM3A and various tumor cells were determined and compared with those in the cell homogenate. Although aminopeptidase (EC 3.4.11.-) activities were always detected on the surface membrane in mammalian cells, trypsin, chymotrypsin and elastase activities were not detected while slight glycosidase activity was detected in a suspension of cultured cells. The activities of alanine-, leucine-, methionine- and phenylalanine-aminopeptidases were rather high but aminopeptidase A, proline-, valine-, glycyl propline dipeptidyl-and glycyl propyl leucine-tripeptidyl-aminopeptidases showed relatively low activities. Aminopeptidase activity was also demonstrated in the isolated membrane fractions. The specific activities of enzymes in these membrane fractions were not significantly greater than in cell homogenate so it was concluded that these enzyme activities were rather loosely bound to the cell membrane. Further evidence for the localization of the aminopeptidase activities on the cell surface was obtained by using glass-bead-bound substrate and detecting the release of the terminal residues. When bestatin, a specific inhibitor against aminopeptidase B and leucine aminopeptidase, was included in the assay system for the enzyme activities on the cell surface, the enzymes were commonly inhibited in all types of cells.
测定了猴肾、犬肾、L. FM3A及各种肿瘤细胞表面水解酶的活性，并与细胞匀浆中的活性进行了比较。尽管在哺乳动物细胞的表面膜上总能检测到氨肽酶（EC 3.4.11.-）的活性，但未检测到胰蛋白酶、糜蛋白酶和弹性蛋白酶的活性，而在培养细胞悬液中检测到了轻微的糖苷酶活性。丙氨酸 - 、亮氨酸 - 、蛋氨酸 - 和苯丙氨酸 - 氨肽酶的活性相当高，但氨肽酶A、脯氨酸 - 、缬氨酸 - 、甘氨酰脯氨酸二肽基 - 和甘氨酰丙基亮氨酸三肽基 - 氨肽酶的活性相对较低。在分离的膜组分中也证实了氨肽酶活性。这些膜组分中酶的比活性并不显著高于细胞匀浆中的比活性，因此得出结论，这些酶活性与细胞膜的结合相当松散。通过使用玻璃珠结合的底物并检测末端残基的释放，获得了氨肽酶活性定位于细胞表面的进一步证据。当在细胞表面酶活性的测定系统中加入氨肽酶B和亮氨酸氨肽酶的特异性抑制剂贝司他汀时，所有类型的细胞中的酶都受到普遍抑制。
