Involved in the biosynthesis of capreomycidine, an unusual amino acid used by non-ribosomal peptide synthases (NRPS) to make the tuberactinomycin class of peptide antibiotic such as viomycin and capreomycin. Catalyzes the dehydration of the C3 hydroxyl of (3S)-hydroxy-(2S)-arginine and the intramolecular cyclization to yield (2S,3R)-capreomycidine. (2S,3S)-hydroxyarginine = (2S,3R)-capreomycidine + H2O Antibiotic biosynthesis. Belongs to the class-II pyridoxal-phosphate-dependent aminotransferase family.