Acts as an alpha-ketoglutarate-dependent dioxygenase catalyzing hydroxylation of glutarate (GA) to L-2-hydroxyglutarate (L2HG). Functions in a L-lysine degradation pathway that proceeds via cadaverine, glutarate and L-2-hydroxyglutarate. 2-oxoglutarate + glutarate + O2 = (S)-2-hydroxyglutarate + CO2 + succinate Binds 1 Fe(2+) ion per subunit. Amino-acid degradation. Homotetramer. Belongs to the glutarate hydroxylase family.