Inhibition of enzymes and oxidative damage of red blood cells induced by t-butylhydroperoxide-derived radicals.
The effects of t-butylhydroperoxide (tBHP), its alkoxyl radical (tBuO.) and its peroxyl radical (tBuOO.) in model systems and on red blood cells were studied. Glyceraldehyde-3-phosphate dehydrogenase was strongly inhibited by tBHP via a direct reaction of the hydroperoxide with an essential sulfhydryl group in the enzyme molecule. Several other enzymes were unaffected by tBHP. Alcohol dehydrogenase was strongly inhibited by tBuO. but was much less sensitive to tBuOO.. Lysozyme, lactate dehydrogenase and trypsin, on the other hand, were very sensitive to the peroxyl and not, or much less, to the alkoxyl radical, whereas acetylcholinesterase was very sensitive to both radicals. tBuOO. caused covalent binding of tryptophan, tyrosine, histidine and methionine to serum albumin. The corresponding alkoxyl radical was ineffective in this respect. Conversely, tBuO. caused peroxidation of linolenic acid, whereas tBuOO. did not. Incubation of human erythrocytes with tBHP caused lipid peroxidation and K+ leakage. Both effects were caused by tBHP-derived radicals generated in a reaction of the hydroperoxide with hemoglobin. With radical scavengers it was possible to dissociate tBHP-induced lipid peroxidation and K+ leakage, demonstrating that these two processes are not causally related. Experimental results indicate that tBuO. causes lipid peroxidation, whereas tBuOO. is responsible for K+ leakage.
Van der Zee
J
J
Sylvius Laboratories, Department of Medical Biochemistry, Leiden, The Netherlands.
Van Steveninck
J
J
Koster
J F
JF
Dubbelman
T M
TM
D000596:Amino Acids / Q000378:metabolism; D004910:Erythrocyte Membrane / Q000187:drug effects; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism*; D005609:Free Radicals; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000037:antagonists & inhibitors*; D006801:Humans; D008054:Lipid Peroxides / Q000096:biosynthesis; D008954:Models, Biological; D010084:Oxidation-Reduction / Q000187:drug effects; D010545:Peroxides / Q000494:pharmacology*; D011188:Potassium / Q000097:blood; D012709:Serum Albumin / Q000378:metabolism; D020122:tert-Butylhydroperoxide
D000596:Amino Acids; D005609:Free Radicals; D008054:Lipid Peroxides; D010545:Peroxides; D012709:Serum Albumin; D020122:tert-Butylhydroperoxide; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D011188:Potassium