Enzymatic and Molecular Biological Analysis of Palmitoyl Protein Thioesterase Deficiency in Infantile Neuronal Ceroid Lipofuscinosis

Publisher Website
Google Scholar
Abstract
Infantile neuronal ceroid lipofuscinosis (INCL) is a neurodegenerative lysosomal storage disease that results from a deficiency of palmitoyl protein thioesterase (PPT), a deacylating enzyme that removes cysteine‐bound palmitate from proteins. We developed an in vitro PPT enzyme assay that can be readily used for the clinical diagnosis of both INCL patients and carriers. The substrate is a palmitoylated peptide (IRY[14C]palmitoyl‐CWLRR) synthesized by reacting [14C]palmitoyl‐CoA with a synthetic octapeptide from the PNS P0 glycoprotein. The PPT assay performed in immortalized lymphoblastoid B‐cells or the postmortem brain homogenate showed the optimal enzyme activity at pH 5.0, consistent with the findings that PPT is a lysosomal enzyme. PPT activity in lymphoblasts from INCL patients was 32P‐labeled PPT by northern blot analysis, the level of transcript varied among independent INCL families and was not related to PPT activity. In conclusion, whereas variant genetic modifications result in PPT deficiency, all giving similar INCL phenotype, both affected patients and heterozygote carriers can now be screened with a reliable in vitro PPT assay.

This publication has 0 references indexed in Scilit: