The function of DOHH (deoxyhypusine hydroxylase, Ensembl gene identifier ENSG00000129932) is as follows. Catalyzes the hydroxylation of the N(6)-(4-aminobutyl)-L- lysine intermediate produced by deoxyhypusine synthase/DHPS on a critical lysine of the eukaryotic translation initiation factor 5A/eIF- 5A. This is the second step of the post-translational modification of that lysine into an unusual amino acid residue named hypusine (PubMed:16371467, PubMed:16533814, PubMed:19706422). Hypusination is unique to mature eIF-5A factor and is essential for its function (By similarity). {ECO:0000250|UniProtKB:Q99LN9, ECO:0000255|HAMAP- Rule:MF_03101, ECO:0000269|PubMed:16371467, ECO:0000269|PubMed:16533814, ECO:0000269|PubMed:19706422}.