As shown in Fig. 4D, a reaction that oxidizes GGOH to GGal showed Michaelis-Menten-type kinetics (Fig. 4D) and the Km value of the recombinant human MAOB was calculated to be 34.34 ± 5.35 μM for GGOH, which is in the range of those of rat hepatic (10) and human hepatoma GGOH oxidase (11). The gene discussed is MAOB; the disease is hepatocellular carcinoma.