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Characterization of Novel Pathogenic Variants Causing Pyridox(am)ine 5'-Phosphate Oxidase-Dependent Epilepsy.

ABSTRACT: Several variants of the enzyme pyridox(am)ine 5'-phosphate oxidase (PNPO), responsible for a rare form of vitamin B₆-dependent neonatal epileptic encephalopathy known as PNPO deficiency (PNPOD), have been reported. However, only a few of them have been characterised with respect to their structural and functional properties, despite the fact that the knowledge of how variants affect the enzyme may clarify the disease mechanism and improve treatment. Here, we report the characterisation of the catalytic, allosteric and structural properties of recombinantly expressed D33V, R161C, P213S, and E50K variants, among which D33V (present in approximately 10% of affected patients) is one of the more common variants responsible for PNPOD. The D33V and E50K variants have only mildly altered catalytic properties. In particular, the E50K variant, given that it has been found on the same chromosome with other known pathogenic variants, may be considered non-pathogenic. The P213S variant has lower thermal stability and reduced capability to bind the FMN cofactor. The variant involving Arg161 (R161C) largely decreases the affinity for the pyridoxine 5'-phosphate substrate and completely abolishes the allosteric feedback inhibition exerted by the pyridoxal 5'-phosphate product.

SUBMITTER: Barile A

PROVIDER: S-EPMC8584306 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:The PDE12 gene codes for the poly(A)-specific exoribonuclease, involved in the quality control of mitochondrial non-coding RNAs. Here, we report that disease-causing PDE12 variants in three unrelated families are associated with mitochondrial respiratory chain deficiencies. Clinically, they presented in utero and within the neonatal period with muscle and brain involvement leading to marked cytochrome c oxidase (COX) deficiency in muscle and severe lactic acidosis. To analyze perturbations in specific cellular pathways contributing to pathogenesis in our patient cohort, we used Affymetrix Clariom D transcriptome arrays to study the RNA levels in fibroblasts derived from two patient (Patient 2 and patient 3), comparing these to age-matched controls.

2024-09-29 | E-MTAB-14251 | biostudies-arrayexpress

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