[Use of alpha-ketobutyrate for the differential determination of the activities of lactate dehydrogenase isoenzyme subunits].

Estimation of alpha-ketobutyrate dehydrogenase activity might be used for quantitative evaluation of LDH isozyme subunits H and M. Empiric constants, which are included in equations for calculation of the activity of subunits and applied for purified human LDH isoenzymes, were not altered in presence of blood serum and were quite reproducible from day to day. Reliability of quantitative differentiation of the activities of H and M subunits by means of alpha-ketobutyrate was demonstrated by analyses of standard LDH isoenzyme mixtures as well as normal and pathological blood sera with typical patterns of LDH isoenzymes. Estimation of activity of the LDH isoenzyme subunits using alpha-ketobutyrat e proved to be rapid, simple and unexpensive method for determination of LDH isoenzyme spectra in physiological fluids.