Wagner B J, Fu S C, Margolis J W, Fleshman K R
Exp Eye Res. 1984 May;38(5):477-83. doi: 10.1016/0014-4835(84)90125-8.
Lens neutral proteinase is thought to exhibit primarily endopeptidase activity. We have identified a synthetic endopeptidase substrate which is hydrolyzed by the bovine lens neutral proteinase preparation. Among 11 fluoro- and chromogenic endopeptidase substrates, only carbobenzoxy-glycylglycyl-L-leucyl-p-nitroanilide is effectively hydrolyzed. The activity hydrolyzing this substrate co-elutes with neutral proteinase activity upon gel filtration and specifically attacks the leucyl-p-nitroaniline bond. Optimal hydrolysis of the synthetic substrate is at neutral pH and high temperature (53 degrees C), analogous to the alpha-crystallin protein substrate obtained from lens. The rate of hydrolysis of the synthetic substrate increased proportionally with temperature between 20 and 60 degrees C, in contrast to alpha-crystallin. The rate of hydrolysis was linear for at least 1 h at 37 degrees C and there was no evidence of enzyme activation at high temperature.
晶状体中性蛋白酶被认为主要表现出内肽酶活性。我们鉴定出一种合成内肽酶底物，它能被牛晶状体中性蛋白酶制剂水解。在11种荧光和显色内肽酶底物中，只有苄氧羰基 - 甘氨酰甘氨酰 - L - 亮氨酰 - 对硝基苯胺能被有效水解。水解该底物的活性在凝胶过滤时与中性蛋白酶活性共洗脱，并特异性攻击亮氨酰 - 对硝基苯胺键。合成底物的最佳水解条件是中性pH和高温（53℃），这与从晶状体获得的α - 晶状体蛋白底物类似。与α - 晶状体蛋白不同，合成底物在20至60℃之间的水解速率随温度成比例增加。在37℃下，水解速率至少1小时呈线性，且没有证据表明在高温下酶被激活。
