The mammalian aromatic amino acid hydroxylases (AAHs), including phenylalanine Hydroxylase (PheOH), tyrosine Hydroxylase (TyrOH) and tryptophan Hydroxylase (TrpOH), are involved in important metabolic pathways neurotransmitters.  Subsequently, defects in biosynthetic pathway have been reported in various neurological disorders such as phenylketonuria, Parkinson's disease, neuropsychiatric syndromes. The lower activities of these enzymes results into lower levels of catecholamine in various neurological diseases states including depression, hypertension and schizophrenia. Therefore, biosynthesis of neurotransmitters is important to study for the identification of aspects of defects in the pathways. In the present study we have utilized single site mutation induced effects on three aromatic amino acid hydroxylases of the metabolism pathway to study effects on biosynthetic pathways. Thus we have utilized atomic coordinates of AAHs, 1MLW, 1DMW, 2TOH and ternary complex, 1MMK from RCSB PDB. The resulting thermodynamic stability of these hydroxylases due to folding energy changes (??G) in wild type and mutated protein was obtained along with total energy of the system. In all four cases, we have analysed two sets for each desired residue: one with highest (+) and lowest (-) ??G (kcal/mol)values. Further preliminary docking studies were done to obtain protein-ligand interactions for mutated residues. MM-GBSA and FEP on most stabilizing and high scored mutation was done for analysis of BH4 binding, iron coordinated active site, substrates specificity determinates residues. Therefore, FEP analysis for investigating conformational changes due to the mutation is provided by the backbone torsion angles phi and psi of the aromatic residues involved in co-factor binding which were later mutated to non-aromatic residues. Our present studies have predicted impact of co-factor mediated mutations on the AAHs biosynthetic pathways.

Importance of tetrahydrobiopterin mediated interactions in aromatic amino acid hydroxylases enzymes family: Assessing effect on biosynthesis due to effect of single site mutation on thermodynamic stability of hydroxylases

247th National Meeting (2014)

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