title: Understanding N-Acetyl-L-Glutamate Synthase Deficiency: Mutational Spectrum, Impact of Clinical Mutations on Enzyme Functionality, and Structural Considerations.
abstract: N-acetyl-L-glutamate synthase (NAGS) deficiency (NAGSD), the rarest urea cycle defect, is clinically indistinguishable from carbamoyl phosphate synthetase 1 deficiency, rendering the identification of NAGS gene mutations key for differentiation, which is crucial, as only NAGSD has substitutive therapy. Over the last 13 years, we have identified 43 patients from 33 families with NAGS mutations, of which 14 were novel. Overall, 36 NAGS mutations have been found so far in 56 patients from 42 families, of which 76% are homozygous for the mutant allele. 61% of mutations are missense changes. Lack or decrease of NAGS protein is predicted for ∼1/3 of mutations. Missense mutations frequency is inhomogeneous along NAGS: null for exon 1, but six in exon 6, which reflects the paramount substrate binding/catalytic role of the C-terminal domain (GNAT domain). Correspondingly, phenotypes associated with missense mutations mapping in the GNAT domain are more severe than phenotypes of amino acid kinase domain-mapping missense mutations. Enzyme activity and stability assays with 12 mutations introduced into pure recombinant Pseudomonas aeruginosa NAGS, together with in silico structural analysis, support the pathogenic role of most NAGSD-associated mutations found. The disease-causing mechanisms appear to be, from higher to lower frequency, decreased solubility/stability, aberrant kinetics/catalysis, and altered arginine modulation.
authors.affiliation: Instituto de Biomedicina de Valencia (IBV-CSIC), Valencia, Spain.
authors.forename: Enea
authors.initials: E
authors.lastname: Sancho-Vaello
authors.affiliation: Instituto de Biomedicina de Valencia (IBV-CSIC), Valencia, Spain.|Group 739, CIBERER, ISCIII, Spain.
authors.forename: Clara
authors.initials: C
authors.lastname: Marco-Marín
authors.affiliation: Instituto de Biomedicina de Valencia (IBV-CSIC), Valencia, Spain.|Group 739, CIBERER, ISCIII, Spain.
authors.forename: Nadine
authors.initials: N
authors.lastname: Gougeard
authors.affiliation: Instituto de Biomedicina de Valencia (IBV-CSIC), Valencia, Spain.|Group 739, CIBERER, ISCIII, Spain.
authors.forename: Leonor
authors.initials: L
authors.lastname: Fernández-Murga
authors.affiliation: University Children's Hospital and Children's Research Center, Zurich, Switzerland.
authors.forename: Véronique
authors.initials: V
authors.lastname: Rüfenacht
authors.affiliation: University Children's Hospital and Children's Research Center, Zurich, Switzerland.
authors.forename: Merima
authors.initials: M
authors.lastname: Mustedanagic
authors.affiliation: Instituto de Biomedicina de Valencia (IBV-CSIC), Valencia, Spain.|Group 739, CIBERER, ISCIII, Spain.
authors.forename: Vicente
authors.initials: V
authors.lastname: Rubio
authors.affiliation: University Children's Hospital and Children's Research Center, Zurich, Switzerland.
authors.forename: Johannes
authors.initials: J
authors.lastname: Häberle
mesh_terms: D051046:Amino-Acid N-Acetyltransferase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D020022:Genetic Predisposition to Disease; D006801:Humans; D008958:Models, Molecular; D020125:Mutation, Missense; D011485:Protein Binding; D000072417:Protein Domains; D055550:Protein Stability; D056806:Urea Cycle Disorders, Inborn / Q000235:genetics*
chemical_list: D051046:Amino-Acid N-Acetyltransferase; C494874:NAGS protein, human
keywords: NAGS; acetylglutamate synthase; argA; inborn errors; site-directed mutagenesis; urea cycle diseases