Automated differentiation and measurement of hexosaminidase isoenzymes in biological fluids and its application to pre- and postnatal detection of Tay-Sachs disease.

Three hexosaminidase (EC 3.2. 1.52) isoenzymes other than isoenzymes A and B in body fluids have been separated by chromatography on diethylaminoethyl cellulose. By inserting a microcolumn into a continuous-flow system for automated, fluorometric hexosaminidase analysis [Clin. Chem. 20, 538 (1974)], samples eluted with buffered-NaCl gradients can be continuously monitored. Isoenzyme patterns were obtained for fluids from normal individuals, pregnant women, Tay-Sachs disease carriers, pregnant carriers, and patients with the disease. These chromatograms revealed a hitherto undetected isoenzyme (I-3) in serum. An increase in serum hexosaminidase isoenzyme I-2 (or P) during pregnancy is characteristic of a carrier pattern. Our data show that serum and urinary hexosaminidase isoenzyme patterns may be used in addition to leukocyte analysis, to distinguish a pregnant carrier from a normal pregnant woman. All fluids tested demonstrated no isoenzyme A activity and above-normal activity of isoenzymes B and (or) I-2 in homozygotes. Urine is preferred fluid for postnatal and amniotic fluid for the prenatal diagnosis of the disease. Quantitative data on isoenzyme A obtained with the procedure described here agree well with those obtained by heat-and pH-inactivation methods.