New variants of AADC deficiency expand the knowledge of enzymatic phenotypes.

Abstract

AADC deficiency is a rare genetic disease caused by mutations in the gene of aromatic amino acid decarboxylase, the pyridoxal 5'-phosphate dependent enzyme responsible for the synthesis of dopamine and serotonin. Here, following a biochemical approach together with an in silico bioinformatic analysis, we present a structural and functional characterization of 13 new variants of AADC. The amino acid substitutions are spread over the entire protein from the N-terminal (V60A), to its loop1 (H70Y and F77L), to the large domain (G96R) and its various motifs, i.e. loop2 (A110E), or a core β-barrel either on the surface (P210L, F251S and E283A) or in a more hydrophobic milieu (L222P, F237S and W267R) or loop3 (L353P), and to the C-terminal domain (R453C). Results show that the β-barrel variants exhibit a low solubility and those belonging to the surface tend to aggregate in their apo form, leading to the identification of a new enzymatic phenotype for AADC deficiency. Moreover, five variants of residues belonging to the large interface of AADC (V60A, G96R, A110E, L353P and R453C) are characterized by a decreased catalytic efficiency. The remaining ones (H70Y and F77L) present features typical of apo-to-holo impaired transition. Thus, defects in catalysis or in the acquirement of the correct holo structure are due not only to specific local domain effects but also to long-range effects at either the protein surface or the subunit interface. Altogether, the new characterized enzymatic phenotypes represent a further step in the elucidation of the molecular basis for the disease.

• Authors: Riccardo Montioli, Giovanni Bisello, Mirco Dindo, Giada Rossignoli, Carla Borri Voltattorni, Mariarita Bertoldi
• Journal: Archives of biochemistry and biophysics (Arch Biochem Biophys) Vol. 682 Pg. 108263 (03 30 2020) ISSN: 1096-0384 [Electronic] United States
• PMID: 31953134 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2020 Elsevier Inc. All rights reserved.

Chemical References

• Aromatic-L-Amino-Acid Decarboxylases
• DDC protein, human

Topics

• Algorithms
• Amino Acid Metabolism, Inborn Errors (genetics)
• Amino Acid Motifs
• Aromatic-L-Amino-Acid Decarboxylases (chemistry, deficiency, genetics)
• Catalysis
• Computational Biology
• Escherichia coli
• Genetic Variation
• Humans
• Kinetics
• Magnetic Resonance Spectroscopy
• Mutagenesis, Site-Directed
• Mutation
• Phenotype
• Protein Domains
• Scattering, Radiation
• Solubility
• Spectrophotometry
• Structure-Activity Relationship
• Temperature