Involved in the ornithine fermentation pathway. Catalyzes the conversion of L-ornithine to D-ornithine (PubMed:19251850, PubMed:10715017). OR could also racemize basic amino acids such as lysine and arginine (PubMed:19251850). Serine, asparagine and alanine could be also converted by OR, but at a lower rate (PubMed:19251850). L-ornithine = D-ornithine kcat is 1660 sec(-1) for L-ornithine as substrate (PubMed:19251850). kcat is 980 sec(-1) for L-ornithine as substrate (PubMed:10715017). Optimum pH is 8.5. Homodimer. Belongs to the alanine racemase family.