title: Overexpression of recombinant human antiquitin in E. coli: partial enzyme activity in selected ALDH7A1 missense mutations associated with pyridoxine-dependent epilepsy.
abstract: Pyridoxine-dependent epilepsy (PDE) is an autosomal recessive disorder characterized by early onset seizures responsive to pyridoxine and caused by a defect in the α-aminoadipic semialdehyde dehydrogenase (antiquitin) gene (ALDH7A1). We selected four PDE-associated missense ALDH7A1 mutations, p.V367F, p.F410L, p.Q425R, and p.C450S, generated them in a recombinant human antiquitin cDNA with expression in E. coli at either 30°C or 37°C. One mutation, p.C450S, demonstrated substantial activity after expression at both temperatures, potentially contributing to milder biochemical and clinical phenotypes. The p.Q425R mutation yielded no activity at either temperature. The other two mutations yielded significant enzymatic activity at 30°C and markedly reduced activity at 37°C. For these latter three mutations, the markedly reduced or absent enzymatic activity resulting from expression at 37°C may be consistent with pathogenicity.
authors.affiliation: Department of Pediatrics, University of British Columbia, Vancouver, BC, Canada; Department of Pathology & Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada. Electronic address: marioncm@mail.ubc.ca.
authors.forename: Marion B
authors.initials: MB
authors.lastname: Coulter-Mackie
authors.affiliation: Department of Pediatrics, University of British Columbia, Vancouver, BC, Canada. Electronic address: sylviatiebout@gmail.com.
authors.forename: Sylvia
authors.initials: S
authors.lastname: Tiebout
authors.affiliation: Department of Pediatrics, University of British Columbia, Vancouver, BC, Canada; Centre for Molecular Medicine and Therapeutics, Vancouver, BC, Canada. Electronic address: cvankarnebeek@cw.bc.ca.
authors.forename: Clara
authors.initials: C
authors.lastname: van Karnebeek
authors.affiliation: Department of Pediatrics, University of British Columbia, Vancouver, BC, Canada. Electronic address: sstockler@cw.bc.ca.
authors.forename: Sylvia
authors.initials: S
authors.lastname: Stockler
mesh_terms: D000444:Aldehyde Dehydrogenase / Q000235:genetics* / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D057075:Enzyme Assays; D004827:Epilepsy / Q000201:enzymology* / Q000235:genetics*; D004926:Escherichia coli; D006801:Humans; D050505:Mutant Proteins / Q000378:metabolism; D020125:Mutation, Missense / Q000235:genetics*; D011994:Recombinant Proteins / Q000378:metabolism*; D012995:Solubility
chemical_list: D050505:Mutant Proteins; D011994:Recombinant Proteins; C089507:ALDH7A1 protein, human; D000444:Aldehyde Dehydrogenase
keywords: Antiquitin; Enzymatic activity; Metabolic epilepsy; Missense mutation; Pyridoxine