The effect of methylglyoxal on the oxygen consumption of mitochondria of both normal and leukaemic leucocytes was tested by using different respiratory substrates and complex specific artificial electron donors and inhibitors. The results indicate that methylglyoxal strongly inhibits mitochondrial respiration in leukaemic leucocytes, whereas, at a much higher concentration, methylglyoxal fails to inhibit mitochondrial respiration in normal leucocytes. Methylglyoxal strongly inhibits ADP-stimulated α-oxoglutarate and malate plus NAD + -dependent respiration, whereas, at a higher concentration, methylglyoxal fails to inhibit succinate and α-glycerophosphate-dependent respiration. Methylglyoxal also fails to inhibit respiration which is initiated by duroquinone and cannot inhibit oxygen consumption when the N,N,Nh,Nh-tetramethyl-p-phenylenediamine by-pass is used. NADH oxidation by sub-mitochondrial particles of leukaemic leucocytes is also inhibited by
The oxygen consumption of leukocyte mitochondria of both healthy donors and leukemic patients was tested by using different respiratory substrates. The results indicate that pyruvate could not be utilized by mitochondria of normal leukocytes, whereas mitochondria of leukemic leukocytes could use pyruvate as a good respiratory substrate. A search for the possible presence of pyruvate dehydrogenase complex (PDC) in leukocytes indicates that this enzyme is apparently absent in mitochondria of normal leukocytes but is quite active in mitochondria of leukemic leukocytes. The absence of PDC in normal leukocyte mitochondria can explain the phenomenon of significant aerobic glycolysis that has been observed in normal leukocytes.z 1998 Federation of European Biochemical Societies.
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