title: Association of β-amyloid peptide fragments with neuronal nitric oxide synthase: Implications in the etiology of Alzheimers disease.
abstract: Neuronal nitric oxide synthase (nNOS) was purified on DEAE-Sepharose anion-exchange in a 38% yield, with 3-fold recovery and specific activity of 5 µmol.min(-1).mg(-1). The enzyme was a heterogeneous dimer of molecular mass 225 kDa having a temperature and pH optima of 40°C and 6.5, K(m) and V(max) of 2.6 μM and 996 nmol.min(-1).ml(-1), respectively and was relatively stable at the optimum conditions (t(½) = 3 h). β-Amyloid peptide fragments Aβ(17-28) was the better inhibitor for nNOS (K(i) = 0.81 µM). After extended incubation of nNOS (96 h) with each of the peptide fragments, Congo Red, turbidity and thioflavin-T assays detected the presence of soluble and insoluble fibrils that had formed at a rate of 5 nM.min(-1). A hydrophobic fragment Aβ(17-21) [Leu(17) - Val(18) - Phe(19) - Phe(20) - Ala(21)] and glycine zipper motifs within the peptide fragment Aβ(17-35) were critical in binding and in fibrillogenesis confirming that nNOS was amyloidogenic catalyst.
authors.affiliation: Department of Biochemistry, Microbiology and Biotechnology, Rhodes University, Grahamstown, South Africa.
authors.forename: Eden
authors.initials: E
authors.lastname: Padayachee
authors.forename: Nosiphiwe
authors.initials: N
authors.lastname: Ngqwala
authors.forename: Chris G
authors.initials: CG
authors.lastname: Whiteley
mesh_terms: D000544:Alzheimer Disease / Q000201:enzymology* / Q000209:etiology; D016229:Amyloid beta-Peptides / Q000737:chemistry / Q000494:pharmacology*; D000818:Animals; D002417:Cattle; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D052248:Nitric Oxide Synthase Type I / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000302:isolation & purification; D010446:Peptide Fragments / Q000737:chemistry / Q000494:pharmacology*; D055550:Protein Stability; D013329:Structure-Activity Relationship; D013696:Temperature
chemical_list: D016229:Amyloid beta-Peptides; D004791:Enzyme Inhibitors; D010446:Peptide Fragments; D052248:Nitric Oxide Synthase Type I