Inhibition and Activation of Human Lactate Dehydrogenase by Urea

The degree of inhibition or activation at 37°C by urea of human lactate dehydrogenase isoenzymes has been established with pyruvate, 2-oxobutyrate, and hydroxypvruvate as substrates. Lactate dehydrogenase activation has been demonstrated in the presence of low concentrations of urea. The protective effect of urea against enzyme inhibition by increased substrate concentrations has also been confirmed. Clinical studies indicate that urea inhibition is a practical and potentially valuable tool in the assessment of LDH isoenzyme patterns at 37°C.