Human Oxygenase Variants Employing a Single Protein FeII Ligand Are Catalytically Active

Aspartate/asparagine-beta-hydroxylase (AspH) is a human 2-oxoglutarate (2OG) and Fe-II oxygenase that catalyses C3 hydroxylations of aspartate/asparagine residues of epidermal growth factor-like domains (EGFDs). Unusually, AspH employs two histidine residues to chelate FeII rather than the typical triad of two histidine and one glutamate/aspartate residue. We report kinetic, inhibition, and crystallographic studies concerning human AspH variants in which either of its Fe-II binding histidine residues are substituted for alanine. Both the H725A and, in particular, the H679A AspH variants retain substantial catalytic activity. Crystal structures clearly reveal metal-ligation by only a single protein histidine ligand. The results have implications for the functional assignment of 2OG oxygenases and for the design of non-protein biomimetic catalysts.

Automated summary

The study on human AspH variants reveals insights into its catalytic mechanism, with implications for the functional assignment of 2OG oxygenases and the design of non-protein biomimetic catalysts. The crystal structures show the metal-ligation by only a single protein histidine ligand, indicating a unique approach in Fe-II binding compared to the typical triad of residues. Both H725A and H679A AspH variants exhibit substantial catalytic activity, highlighting their potential applications.