Oxidation of α-hydroxy acids by D-2-hydroxyglutarate dehydrogenase enzymes.

Abstract

α-Hydroxy acids are naturally occurring organic molecules with various medical and industrial applications. However, some α-hydroxy acids, like D-2-hydroxyglutarate (D2HG), have been implicated in cancers and neurometabolic disorders such as D2HG aciduria. Several studies on the D2HG oxidizing enzyme D-2-hydroxyglutarate dehydrogenase (D2HGDH) from various eukaryotic and prokaryotic sources focus on the use and application of the enzyme as biosensors for detecting D2HG. A recent gene knockout study on the bacterial D2HGDH homologs from Pseudomonas stutzeri and Pseudomonas aeruginosa identified the D2HGDH to be essential for bacterial survival by driving L-serine biosynthesis. Thus, D2HGDH is a good candidate for a therapeutic target against the multidrug-resistant P. aeruginosa. However, there is no consensus on the D2HGDH catalytic mechanism, and several D2HGDH homologs have not been characterized in their structural properties, which are two crucial features for therapeutic design. P. aeruginosa D2HGDH, the most extensively studied D2HGDH homolog, is emerging as a paradigm for D2HGDH and flavoproteins with metals in their active site. In this review, we have explored the structures of all published D2HGDH homologs from 12 species using AlphaFold 3 and highlighted the fully conserved structure and active site topologies of all D2HGDH homologs. Additionally, evolutionary and functional studies coupled with analyses of enzymatic activities reveal that prokaryotic and eukaryotic D2HGDH homologs, diverging from two distinct ancestors, may have differentially evolved to specialize in their α-hydroxy acid catalysis. Additionally, this review identifies all D2HGDH homologs as metal and FAD-dependent enzymes that employ a metal-triggered FAD reduction in their catalysis. Elucidation of the D2HGDH mechanism will allow designing antibiotics that target these enzymes as potential therapeutics against pathogenic bacteria like P. aeruginosa in addition to the application of D2HGDH homologs as biosensors.