Liou T G, Campbell E J
Department of Medicine, University of Utah Health Sciences Center, Salt Lake City 84132, USA.
J Immunol. 1996 Sep 15;157(6):2624-31.
Proteinase inhibitors confine the activity of proteolytic enzymes of inflammatory cells, but fail to protect substrates in the immediate pericellular zone. We report quantitative imaging that demonstrates discrete, evanescent, quantized proteolytic events attributable to the release of single azurophil granules from neutrophils. The images provide information about the dynamics of this nonequilibrium system, which is characterized by overwhelmingly high local concentrations of enzymes that rapidly dissipate. With physiologic concentrations of extracellular human leukocyte elastase inhibitors (32.8 microM), the radii of the unit proteolytic events are 1.32 microm (approximately 8 times the radius of the azurophil granule) and are inversely and nonlinearly related to the concentration of proteinase inhibitor that is present in the bathing medium. We have obtained identical results with alpha1-antitrypsin, alpha2m, recombinant secretory leukocyte proteinase inhibitor, and ICI 200,355, and we have found that phagocyte-derived oxidants are not required for the genesis of this catalytic activity. Our results reveal that the enzyme:inhibitor ratio is the primary delimiter of quantized proteolysis in the local microenvironment.
蛋白酶抑制剂可限制炎症细胞中蛋白水解酶的活性，但无法保护紧邻细胞周围区域的底物。我们报告了定量成像结果，该成像显示了离散的、短暂的、量子化的蛋白水解事件，这些事件归因于中性粒细胞单个嗜天青颗粒的释放。这些图像提供了有关这个非平衡系统动力学的信息，该系统的特征是局部酶浓度极高且迅速消散。在细胞外人类白细胞弹性蛋白酶抑制剂的生理浓度（32.8 microM）下，单个蛋白水解事件的半径为1.32微米（约为嗜天青颗粒半径的8倍），并且与浴液中存在的蛋白酶抑制剂浓度呈反比且非线性相关。我们使用α1-抗胰蛋白酶、α2m、重组分泌型白细胞蛋白酶抑制剂和ICI 200,355均得到了相同的结果，并且我们发现这种催化活性的产生不需要吞噬细胞衍生的氧化剂。我们的结果表明，酶与抑制剂的比例是局部微环境中量子化蛋白水解的主要限定因素。
