In vitro effect of elastase and cathepsin G from human neutrophils on creatine kinase and lactate dehydrogenase isoenzymes
Stark, J.A.; Henderson, A.R.
Clinical Chemistry 39(6): 986-992
1993
ISSN/ISBN: 0009-9147 PMID: 8389261 Document Number: 406932
The polymorphonuclear granulocyte, or neutrophil, has been implicated as a mediator of tissue-destructive events because it releases the preformed proteolytic enzymes elastase and cathepsin G, and, as a result of myeloperoxidase action, hypochlorous acid. We show that elastase inactivates and fragments creatine kinase isoenzymes CK-2 and CK-3, and, to a lesser extent, lactate dehydrogenase (LD) isoenzyme LD-1, whereas cathepsin G acts only on CK-2. Both neutrophil enzymes act on LD-3. The course of inactivation was followed by measuring the loss of catalytic activity at 37 degree C. The evidence for fragmentation was obtained by gel filtration; electrophoresis after sample treatment with sodium dodecyl sulfate and 2-mercaptoethanol was less satisfactory for this purpose. Hypochlorous acid inactivates CK activity by about 75% at concentrations as low as 8 mu-mol/L and totally at concentrations gt 140 mu-mol/L, whereas LD activity is not affected until concentrations exceed 200 mu-mol/L. After a myocardial infarction, the number of neutrophils increases; they are triggered and concentrate around damaged myocardial tissue. Our data suggest that neutrophils may inactivate and fragment "cardiac" enzymes released from such damaged tissue.