neurological diseases lead to upregulation of PNPO, immunoreactivities are mainly increased in glutamatergic principal neurons, dentate granule cells and CA1 pyramidal cells, and astrocytes independently of 4-aminobutyric acid levels, overview
the enzyme (PNPO) is upregulated in patients with invasive ductal carcinoma (IDC) and is correlated with the overall survival of patients with metastasis at the later stages
the enzyme catalyzes the last step is pyridoxine 5'-phosphate oxidation to pyridoxal 5'-phosphate. The enzyme plays a pivotal role in controlling intracellular homeostasis and bioavailability of pyridoxal 5'-phosphate
a glutamine amidotransferase consisting of the synthase Pdx1 and its glutaminase partner, Pdx2, form a complex that directly synthesizes pyridoxal from ribose 5-phosphate, glyceraldehyde 3-phosphate, and glutamine. The protein complex displays an ornate architecture consisting of 24 subunits, two hexameric rings of 12 Pdx1 subunits to which 12 Pdx2 subunits attach, with the glutaminase and synthase active sites remote from each other
fluorescence spectrophotometry is used to demonstrate that the Pdx1 C-terminus is indispensable for pyridoxal synthase activity and mediates intersubunit cross-talk within the enzyme complex. The C-terminus can act as a flexible lid, bridging as well as shielding the active site of an adjacent protomer in Pdx1. Ribose 5-phosphate binding triggers strong cooperativity in Pdx1, and the affinity for this substrate is substantially enhanced upon interaction with the Michaelis complex of Pdx2 and glutamine
upregulation of PNPO expression may be involved in dendritic spine reorganization, which in turn, promotes the reverberation of recurrent excitatory networks in the hippocampus following status epilepticus. Activity-dependent regulation of PLP synthetic enzyme levels may play a role in tissue excitability in the hippocampus via various pathways