A new simple enzyme assay for pre- and postnatal diagnosis of infantile neuronal ceroid lipofuscinosis (INCL) and its variants

Pahmitoyl-protein thioesterase (PPT) deficiency was recently shown to be th e primary defect in infantile neuronal ceroid lipofuscinosis (INCL). The av ailable enzyme assay is complicated and impractical for diagnostic use and is, in practice, unavailable. We have developed a new fluorimetric assay fo r PPT based on the sensitive fluorochrome 4-methylumbelliferone. This PPT a ssay is simple, sensitive, and robust and will facilitate the definition of the full clinical spectrum associated with a deficiency of PPT. PPT activi ty was readily detectable in fibroblasts, leucocytes, lymphoblasts, amnioti c fluid cells, and chorionic villi, but was profoundly deficient in these t issues from INCL patients. Similarly, a deficiency of PPT was shown in pati ents with the variant juvenile NCL with GROD. These results show that rapid pre- and postnatal diagnosis can be performed with this new enzyme assay f or PPT.