Ouantitation of High-Density Lipoprotein Cholesterol in Serum by a HeparIn-Mn2 Precipitation

In the assay for hexosaminidase A (Hex A) in leukocytes, cultured fibroblasts, and cultured amniotic fluid cells for the detection of Tay-Sachs disease and carrier identification, bovine serum albumin (BSA) is used (1,2). We find that some BSA preparations are contaminated with hexosaminidase activity. We wish to warn others of this and to show how an incorrect diagnosis could be reached by using contaminated BSA. The 15 leukocyte samples used in the study had less than 50% Hex A when assayed with BSA (Pentex, Miles Laboratories) having no measurable Hex activity. Assay methods were as described by Kaback (2). The average total activity (Table 1) varied considerably between different ESA preparations; the average percent Hex A varied much less, although significantly. When assayed for Hex activity, both Sigma products contained significant amounts; whereas, there was no measurable activity in the Pentex sample. Most of the BSA Hex activity was heat inactivated at pH 4.4 and 52 #{176}C, indicating the presence of “A-like” activity. In addition, electrophoresia of the enzyme on cellulose acetate (Cellogel) resulted in a diffuse band of activity having “A-like” mobility. Because cultured amniotic fluid cells and leukocytes utilize BSA in the assay procedures for Hex A, results could be disastrous if BSA were used that has hexosaminidase activity. A small amount of this “A-like” contaminant