Structural and Functional Consequences of Mutations in 6-Pyruvoyltetrahydropterin Synthase Causing Hyperphenylalaninemia in Humans

Abstract

Four naturally occurring mutants with single amino acid alterations in human 6-pyruvoyltetrahydropterin synthase (PTPS) were overexpressed and characterized in vitro. The corresponding DNA mutations were found in patients with hyperphenylalaninemia and monoamine neurotransmitter insufficiency due to lack of the tetrahydrobiopterin biosynthetic enzyme PTPS. To predict the structure of the mutant enzymes, computer modeling was performed based on the solved three-dimensional structure of the homohexameric rat enzyme. One mutant (delta V57) is incorrectly folded and thus unstable in vitro and in vivo, while a second mutant (P87L) has substantial activity but enhanced sensitivity to local unfolding. Two other mutants, R16C and R25Q, form stable homomultimers and exhibit significant activity in vitro but no activity in COS-1 cells. In vivo 32P labeling showed that wild-type PTPS, P87L, and R25Q are phosphorylated, while R16C is not modified. This strongly suggests that the serine 19 within the consensus sequence for various kinases, RXXS, is the site of modification. Our results demonstrate that PTPS undergoes protein phosphorylation and requires additional, not yet identified post-translational modification(s) for its in vivo function.

Mutation spectrum of and founder effects affecting the PTS gene in East Asian populations

“…30 The founder events and mutations in East Asia To examine the possibility of founder event effects involving the PTS common mutations observed in East Asia, the haplotype of mutations in conjunction with D11S1347 alleles were evaluated by DNA analysis for samples where samples from the parents of probands were available. There were 43 (Table 2, Po0.01 for all groups). The c.84-291A4G mutation was statistical significant linked to the 198 bp allele (P¼0.0008), but not the 194 bp allele (P¼0.0531), although the number of these two haplotypes was equal (n¼7 in both types).…”

Regulation of Tetrahydrobiopterin Biosynthesis by Shear Stress

“…The GTPCH-1 and PTPS antibody are described elsewhere. 18,19 An alternate GTPCH-1 antibody was kindly provided by Irmgard Tegeder (University of Frankfurt, Germany). SR antibody was provided by Young Shik Park (Inje University, Kimhae, South Korea).…”

Bioinformatics Approaches to the Functional Profiling of Genetic Variants

“…There are multiple potential explanations. One is that the structure of PTPS shows the exposure of both R16 and S19 on the surface of the protein ( 3, right; [34]) that forms the consensus sequence R 16 XXS 19 for cGMP protein kinase II. The substitution C16 disrupts this kinase-recognizable motif and thus hinders phosphorylation, which ultimately leads to the inactivation of PTPS.…”