This sequence is similar to that proposed for the metabolism of itaconate by liver mitochondria a but differs from that suggested for itaconate utilization by another pseudomonad 4. Investigations into the nature of enzyme D, which is believed to catalyse the direct formation of itaconyl-CoA from itaconate, ATP and CoA, and into the properties of the enzymes here reported, are continuing. We thank Mr. R. ILEY for technical assistance.
Erythrocyte preparations from normal men and women contain 5 isoenzymes of lactate dehydrogenase in constant proportions. LDH-5 is found exclusively in younger cells, and LDH-1 is the predominant fraction of aged erythrocytes. The apparent increase of LDH-1 in aged cells represents loss of activity of isoenzymes containing labile M subunits and not synthesis of H subunits.
When erythrocyte isoenzymes from patients with hematologic disease are assayed, increases in LDH-5 indicate active or hyperactive erythroid tissue, and absence of this fraction suggests nonfunctioning tissue. An increase in the relative percentage of LDH-1 suggests the presence of an older cell population. Thus the analysis of erythrocyte LDH isoenzymes appears to have clinical value in rapidly assessing erythropoietic activity.
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