Localization of antibacterial activity and hydrolytic enzymes in subcellular fractions of rabbit and chicken...

Polymorphonuclear leukocytes of rabbits and chickens after homogenization in 0.34 M saccharose or after multiple freezing and thawing were subjected to differential centrifugation at 150, 800, 10 000 and 50 000 X g. In the fractions obtained in this manner, total bactericidal activity as well as the activity of myeloperoxidase (E.C. 1. 11. 1. 7), catalase (E.C. 1.11.1.6), lysozyme (E.C. 3.2.1.17), cathepsin D (E.C. 3.4.4.23) and E, beta-D-glucuronidase (E.C. 3.2.1.31) and acid phosphatase (E.C. 3.1.3.2) were determined. Antibacterial activity was found in all fractions from rabbit leukocytes, but only in the first fraction from chick leukocytes. The fractions from rabbit leukocytes contained all enzymes under study while in the fractions from chicken leukocytes the presence of myeloperoxidase, catalase or cathepsin E could not be demonstrated. The highest bactericidal activity was found in the second obtained from the homogenate or rabbit leukocytes. The highest specific activity of myeloperoxidase and homogenate of rabbit leukocytes. The highest specific activity of myeloperoxidase and the lowest activity of cathepsin D were also demonstrated in this fraction. The addition of pepstatin to rabbit leukocytes before their disintegration resulted in the inhibition of the activity of cathepsin D and E and in an increase in the specific activity of myeloperoxidase as well as in total bactericidal activity in the individual fractions. These results testify that microbicidal mechanisms of phagocytes from individual species may differ and when the structure of lysosomes is damaged, the liberated hydrolytic enzymes may gradually inactivate antibacterial substances.