Genetic Variation of Lysosomal Acid Lipase

Extract: Lysosomal acid lipase (LAL) activity was measured using a new fluorometric assay in cultured skin fibroblasts from eight control subjects, two obligate heterozygotes for Wolman's disease (WD), one patient with WD, and one patient with cholesteryl ester storage disease (CESD). The LAL activities (mean ± SD) were 25.8 ± 8.2, 13.2 ± 0.1, 1.1, and 1.4 nmol 4-methylumbelliferyl oleate (4-MUO) hydrolyzed/min/mg protein, respectively. These results compare favorably with those obtained using standard radioassays. The LAL activities of two cultures of amniotic fluid cells were 12.1 and 10.5. The LAL activity (mean ± SD) of peripheral leukocytes obtained from 34 laboratory volunteers (19 females, 15 males) was 4.0 ± 1.8. Partially purified lymphocytes contained about 25 times as much LAL activity as did granulocytes. Cellogel electrophoresis, followed by staining with 4-MUO, showed at least two bands of LAL (A and B) from normal fibroblasts, amniotic fluid cells, and lymphocytes. Band A was absent from WD and CESD fibroblasts and was reduced in fibroblasts of the WD heterozygotes.