“…(B) The functional PAH tetramer and a monomer illustrating the distribution of our selected variants across the structure (PDB: 5DEN). (C) Biophysical calculations with FoldX estimate the effect of each possible single amino acid change on protein stability (ΔΔG), with the results for residues 30-70 shown here, and those for all 420 structural-resolved residues available in the Supporting Information protein function, for example, by changes in the active or cofactorbinding sites, it has been shown that, in general, most missense variant proteins are less structurally stable than the corresponding wild-type protein (Matreyek et al, 2018;Tokuriki, Stricher, Schymkowitz, Serrano, & Tawfik, 2007). Thus, a likely mechanism for the loss of function of many missense variants is loss of stability (Casadio, Vassura, Tiwari, Fariselli, & Luigi, 2011;Yue, Li, & Moult, 2005), leading to increased proteasomal degradation and thus insufficient amounts of PAH protein.…”