Alpha-ketoglutarate-dependent dioxygenase that in vitro catalyzes the regio- and stereoselective hydroxylation of L-ornithine and L-arginine, leading to (3S)-3-hydroxy-L-ornithine and (3S)-3-hydroxy-L-arginine, respectively. Cannot use L-lysine, D-ornithine, or D-arginine as substrate. 2-oxoglutarate + L-ornithine + O2 = (3S)-3-hydroxy-L-ornithine + CO2 + succinate 2-oxoglutarate + L-arginine + O2 = (2S,3S)-hydroxyarginine + CO2 + succinate Binds 1 Fe(2+) ion per subunit. Being totally regio- and stereoselective, this enzyme is of interest for biocatalytic purposes to produce chiral scaffolds that are of synthetic value in the preparation of more complex functionalized chiral molecules such as natural products and analogs. Belongs to the clavaminate synthase family.