A rapid fluorogenic palmitoyl-protein thioesterase assay: Pre- and postnatal diagnosis of INCL

A deficiency of palmitoyl-protein thioesterase (PPT) was recently shown to be the primary defect in infantile neuronal ceroid lipofuscinosis (INCL). T he available enzyme assays are complicated and impractical for diagnostic u se. We have recently developed a new, fluorometric assay for PPT based on t he sensitive fluorochrome 4-methylumbelliferone, requiring an overnight inc ubation to measure PPT, Now we have synthesized an analogue of this substra te which allows PPT determinations in 1 h. This improved PPT assay is simpl e, sensitive, and robust and will. facilitate the definition of the full cl inical spectrum associated with a deficiency of PPT. PPT activity was readi ly detectable in fibroblasts, leukocytes, amniotic fluid cells, chorionic v illi, plasma, and cerebrospinal fluid from controls. PPT activity was profo undly deficient in these tissues and fluids from INCL patients. Similarly, a deficiency of PPT activity was demonstrated in patients with the variant juvenile NCL with GROD. These results show the feasibility of rapid pre- an d postnatal diagnosis of INCL and its variants. (C) 1999 Academic Press.