Pharmacological Chaperones that Protect Tetrahydrobiopterin Dependent Aromatic Amino Acid Hydroxylases Through Different Mechanisms.

The aromatic amino acid hydroxylase (AAAH) enzyme family includes phenylalanine hydroxylase (PAH), tyrosine hydroxylase (TH) and the tryptophan hydroxylases (TPH1 and TPH2). All four members of the AAAH family require iron, dioxygen and the cofactor (6R)-L-erythro-5,6,7,8-tetrahydrobiopterin (BH4) to hydroxylate their respective substrates. The AAAHs are involved in severe diseases; whereas polymorphisms and variants in the TPH genes are associated to neuropsychiatric disorders, mutations in PAH and TH are responsible for the autosomal recessive disorders phenylketonuria (PKU) and TH deficiency (THD), respectively.

Brain catecholamine depletion and motor impairment in a Th knock-in mouse with type B tyrosine hydroxylase deficiency.

Tyrosine hydroxylase catalyses the hydroxylation of L-tyrosine to l-DOPA, the rate-limiting step in the synthesis of catecholamines. Mutations in the TH gene encoding tyrosine hydroxylase are associated with the autosomal recessive disorder tyrosine hydroxylase deficiency, which manifests phenotypes varying from infantile parkinsonism and DOPA-responsive dystonia, also termed type A, to complex encephalopathy with perinatal onset, termed type B. We generated homozygous Th knock-in mice with the mutation Th-p.

Discovery of compounds that protect tyrosine hydroxylase activity through different mechanisms.

Pharmacological chaperones are small compounds that correct the folding of mutant proteins, and represent a promising therapeutic strategy for misfolding diseases. We have performed a screening of 10,000 compounds searching for pharmacological chaperones of tyrosine hydroxylase (TH), the tetrahydrobiopterin (BH4)-dependent enzyme that catalyzes the rate-limiting step in the synthesis of catecholamines. A large number of compounds bound to human TH, isoform 1 (hTH1), but only twelve significantly protected wild-type (hTH1-wt) and mutant TH-R233H (hTH1-p.