Cathepsin G from Human Neutrophils, 100æg

Cathepsin G is a serine protease that degrades collagen and proteoglycans. It has been implicated in connective tissue-related disorders. Cathepsin G from human leukocytes is a glycoprotein containing approximately 1% carbohydrate. It is considered to be a major constituent of human neutophil granulocytes. The enzyme is sequestered in the matrix of the granules and is only released during phagocytosis. However, upon neutrophil cell death, the enzyme may leak from the vacuole. When levels of specific inhibitor are not high enough to inhibit the released enzyme, tissue damage may occur involving the degradation of connective tissue proteins. Cathepsin G act as a bacteriocidal reagent. Cathepsin G is often referred to as a chymotrypsin-like enzyme, since it preferentially cleaves proteins on the carboxyl side of leucine, methionine, and phenylalanine. Cathepsin G can be assayed with substrates such as azocasein, Suc-Ala-Ala-Pro-Phe-NPhNO2, and MeOSUC-Ala-Ala-Pro-Met-NPh-NO2. Cathepsin G also has a specificity of action on the oxidized B chain of insulin and on BSA, which indicates a closer similarity to porcine chymotrypsin C than to bovine chymotrypsin A. Cathepsin G has pro-apoptotic activity and can activate caspases in vitro.