Eisenhauer D A, Berger J J, Peltier C Z, Taylor A
USDA Human Nutrition Research Center on Aging, Tufts University, Boston, MA 02111.
Exp Eye Res. 1988 Apr;46(4):579-90. doi: 10.1016/s0014-4835(88)80014-9.
Beef lens cells in culture are readily obtained and provide many opportunities to study phenomena related to cell differentiation and maturation, environmental stress, disease, and perhaps mechanisms of transformation. Although altered rates of proteolysis are known to accompany these phenomena, the proteolytic activities available in cultured beef lens epithelial cells have not been documented. In this work are documented the specific activities, based on protein and DNA content, of neutral exo- and endopeptidase, cathepsins B- and D-like enzymes and acid phosphatase in lens epithelial cortical and core tissue and in cultured epithelial cells at passages 1-43. Maximal activity of each protease occurs almost routinely at passage 5 or 9, reaching values of approx. 1400-, 0.77-, 4520-nmol min-1 per mg protein for neutral exopeptidase (passage 5), neutral endopeptidase (passage 5) and cathepsin B (passage 5) respectively, and 7.1 micrograms trichloroacetic acid soluble peptide min-1 per mg protein for cathepsin D (passage 15). On a microgram-1 DNA basis, the maximal specific activities for the same enzymes were 48 (passage 5), 0.03 (passage 5), 283 (passage 9), and 0.5 (passage 9) respectively. In subsequent passages, the specific activities declined to values which were similar to or lower than the specific activities observed for these proteases in lens epithelial tissue.
培养中的牛晶状体细胞很容易获得，为研究与细胞分化和成熟、环境应激、疾病以及可能的转化机制相关的现象提供了许多机会。尽管已知蛋白水解速率的改变伴随着这些现象，但培养的牛晶状体上皮细胞中可用的蛋白水解活性尚未见报道。在这项工作中，记录了晶状体上皮皮质和核心组织以及传代1 - 43次的培养上皮细胞中基于蛋白质和DNA含量的中性外肽酶和内肽酶、组织蛋白酶B和D样酶以及酸性磷酸酶的比活性。每种蛋白酶的最大活性几乎都在传代5或9时出现，中性外肽酶（传代5）、中性内肽酶（传代5）和组织蛋白酶B（传代5）的活性分别达到约1400、0.77、4520 nmol min-1 per mg蛋白质，组织蛋白酶D（传代15）的活性为7.1微克三氯乙酸可溶性肽min-1 per mg蛋白质。以每微克-1 DNA为基础，相同酶的最大比活性分别为48（传代5）、0.03（传代5）、283（传代9）和0.5（传代9）。在随后的传代中，比活性下降到与晶状体上皮组织中这些蛋白酶观察到的比活性相似或更低的值。
