| 2005 |
PNPO encodes pyridox(am)ine 5'-phosphate oxidase, the enzyme responsible for converting pyridoxamine 5'-phosphate and pyridoxine 5'-phosphate to pyridoxal 5'-phosphate (PLP). Splice site (IVS3-1g>a) and stop codon (X262Q) mutations in PNPO were null activity mutations, and the missense mutation R229W markedly reduced enzymatic activity, as demonstrated by expression studies in Chinese hamster ovary cells. |
Expression studies in CHO cells, enzymatic activity assays, PNPO gene sequencing |
Human molecular genetics |
High |
15772097
|
| 1998 |
PNPO cDNA encodes a functional pyridoxine-5'-phosphate oxidase; stable transfection of PNPO-negative hepatoma cell lines with the PNPO cDNA restored enzymatically active PNPO protein, confirming the cDNA encodes the rate-limiting enzyme in PLP biosynthesis. The translated product was immunologically reactive to a polyclonal PNPO antibody. |
Stable transfection of PNPO-negative hepatoma cell lines, enzymatic activity assay, immunological verification |
Biochemistry |
High |
9601034
|
| 2014 |
Novel PNPO sequence changes, including R225H/C and D33V mutations, were shown to reduce enzyme activity using a cell-free expression system and a mass spectrometry-based assay for pyridoxamine phosphate oxidase. Many mutations affected residues involved in binding FMN (cofactor) or PLP (product), establishing structure-function relationships for these residues. |
Cell-free expression system, mass spectrometry-based enzymatic assay |
Brain : a journal of neurology |
Medium |
24645144
|
| 2014 |
The PNPO missense mutations p.Arg225His and p.Arg141Cys, and the deletion c.279_290del, were shown to reduce enzymatic activity by expression studies in CHO-K1 cell lines, establishing their pathogenicity. These mutations were absent in 100 control alleles. |
Expression studies in CHO-K1 cell lines, enzymatic activity assay |
Neurology |
Medium |
24658933
|
| 2008 |
The novel PNPO mutation c.284G>A (p.Arg95His) in exon 3 reduces PNPO mutant enzymatic activity to 18% relative to wild type, as demonstrated by expression studies. |
Expression studies, enzymatic activity assay |
Molecular genetics and metabolism |
Medium |
18485777
|
| 2017 |
The Arg116Gln PNPO variant, expressed as recombinant protein, does not alter overall enzyme structure but reduces affinity for the cofactor FMN, reduces thermal stability, slightly affects catalytic efficiency, and impairs transfer of PLP to PLP-dependent enzymes, establishing a mechanistic basis for partial loss of function. |
Recombinant protein expression, structural and kinetic characterization, FMN and PLP binding constants, thermal stability assay |
Molecular genetics and metabolism |
High |
28818555 29379851
|
| 2019 |
In Drosophila, silencing the PNPO ortholog sgll (sugarlethal) by RNAi causes chromosome aberrations in neuroblasts and induces diabetic hallmarks (hyperglycemia, small body size). Chromosome aberrations are largely caused by the genotoxic effect of advanced glycation end products triggered by high glucose, establishing that PNPO/PLP is required for both DNA integrity and glucose homeostasis. |
RNAi knockdown in Drosophila, chromosome aberration analysis, glucose measurement |
Journal of cellular physiology |
Medium |
31506944
|
| 2019 |
CRISPR/Cas9-generated pnpo-/- zebrafish show reduction of PLP and pyridoxal with accumulation of PMP and pyridoxamine, confirming PNPO catalyzes the oxidation of PNP and PMP to PLP in vivo. Decreased GABA and glutamate result from impaired PLP-dependent enzyme activity. PLP treatment normalized PLP, glutamate, GABA, and glycine levels but did not normalize all amino acid profiles, suggesting additional roles for PMP accumulation in the disease phenotype. |
CRISPR/Cas9 knockout zebrafish, biochemical profiling (B6 vitamers, amino acids, neurotransmitters), PLP rescue |
Biochimica et biophysica acta. Molecular basis of disease |
High |
31759955
|
| 2019 |
Zebrafish pnpo knockdown (morpholino) causes brain malformation and impaired locomotor activity. These phenotypes are rescued by co-injection of zpnpo or hPNPO mRNA, or by PLP supplementation. Pyridoxamine (PM) supplementation showed rescue effects at lower concentrations than PLP, suggesting PM as an alternative substrate/therapeutic route. GABA supplementation also showed partial rescue, placing PNPO upstream of GABA synthesis. |
Morpholino knockdown in zebrafish, mRNA rescue, pharmacological supplementation, behavioral assay |
Frontiers in pharmacology |
Medium |
31616300
|
| 2022 |
CRISPR-Cas9 knock-in Drosophila alleles carrying human PNPO epilepsy-associated variants (h116, h33, h95) exhibit allele-dependent phenotypes (developmental impairments, seizures, shortened lifespan) correlating with the known biochemical severity of each mutation. The hR95H allele has a dominant-negative effect, rendering heterozygous flies susceptible to seizures and premature death. PLP supplementation prevented developmental impairments and seizures. |
CRISPR-Cas9 knock-in Drosophila, behavioral analysis, PLP dietary supplementation rescue |
Proceedings of the National Academy of Sciences of the United States of America |
High |
35217610
|
| 2024 |
PNPO acts as an oxygen sensor in macrophages: decreased PNPO activity under prolonged hypoxia reduces PLP levels, inhibiting lysosomal acidification. This leads to iron dysregulation, TET2 protein loss, and delayed resolution of inflammatory response. Among PLP-dependent metabolic pathways, supersulfide synthesis is specifically suppressed under prolonged hypoxia, mechanistically linking PNPO activity to lysosomal function and macrophage inflammatory phenotype. |
Macrophage hypoxia model, PNPO activity assay, lysosomal acidification assay, iron and TET2 protein measurement, supersulfide metabolite profiling |
Nature metabolism |
High |
38822028
|
| 2024 |
PNPO oxidizes disheveled 3 at Met282 (DVL3M282), leading to abnormal activation of the Wnt/β-catenin pathway in multiple myeloma cells. Critical PNPO residues R95 and K117 are required for interaction with DVL3. Disrupting the PNPO-DVL3 interaction (with Eltrombopag) inhibited MM cell growth and reduced bone lesions in mouse models. |
Celastrol probe target identification, co-IP/interaction studies, mutagenesis of PNPO (R95, K117), Wnt/β-catenin pathway reporter, mouse xenograft model, DVL3 oxidation assay |
Advanced science (Weinheim, Baden-Wurttemberg, Germany) |
Medium |
39656865
|
| 2024 |
PNPO promotes lysosomal biogenesis and perinuclear distribution, enhancing autophagic flux in ovarian cancer cells via a PNPO-LAMP2 axis. LAMP2 silencing blocked PNPO's effect on cellular processes. PNPO also regulates cell cycle progression via cyclin B1 and phosphorylated CDK1. |
siRNA knockdown, overexpression, LAMP2 co-silencing, cell cycle analysis, xenograft tumor model |
Apoptosis : an international journal on programmed cell death |
Medium |
38615082
|
| 2025 |
In Drosophila sgll (PNPO ortholog) mutants, cell-autonomous expression of human PNPO cDNA specifically in GABAergic neurons largely restored lifespan and attenuated seizure activity, while expression in cholinergic or glutamatergic neurons did not. Glial expression provided partial rescue. GABA-B agonist SKF-97541 (but not GABA-A modulators) reduced mortality, establishing that PNPO acts cell-autonomously in GABAergic neurons to support brain function. |
Cell-type-specific hPNPO cDNA rescue in Drosophila sgll mutants, survival and seizure behavioral assays, pharmacological GABA receptor modulation |
Journal of neurogenetics |
High |
41296493
|
| 2025 |
In Drosophila PNPO (sgll) mutants, PNPO deficiency reduces alcohol aversion, increases alcohol consumption, and alters locomotor behavior. Biochemically, both PNPO deficiency and alcohol exposure elevate GABA and glycine. VB6 supplementation rescues lethality caused by combined PNPO deficiency and alcohol, establishing a functional interaction between genetic VB6 deficiency and alcohol at the level of inhibitory neurotransmitter metabolism. |
Drosophila PNPO mutant model, behavioral assays (alcohol aversion, consumption, locomotion), amino acid/neurotransmitter metabolomics, VB6 supplementation rescue |
bioRxivpreprint |
Medium |
bio_10.1101_2025.03.06.641947
|