A rapid method for assay of branched-chain keto acid decarboxylation in cultured cells and its application to prenatal diagnosis of maple syrup urine disease.

A sensitive assay for measurement of branched-chain keto acid decarboxylation in small numbers of fibroblasts or amniotic cells grown in the wells of a microtitre plate using [1-14C]leucine as substrate is described. The method was applied to the amniotic cells from a pregnancy at risk for maple syrup urine disease and a heterozygous fetus predicted.