Both isoforms have a higher affinity for ornithine (Km 0.2 and 0.4 mM for ORC1 and ORC2, respectively) than for lysine or L-arginine (0.8 and 1.6 mM for ORC1 and ORC2, respectively) [96], although whether their expression level is increased in M1 macrophages or HCC cells remains to be investigated. Here, ORC1 is linked to hepatocellular carcinoma.