Pathway of glutamate oxidation and its regulation in the HuH13 line of human hepatoma cells.
Well-coupled mitochondria were isolated from a HuH13 line of human hepatoma cells and human liver tissue. The liver mitochondria showed a feeble glutamine oxidation activity in contrast to the hepatoma mitochondria, whereas they utilized glutamate well for the oxidative phosphorylation. In the liver mitochondria, glutamate was oxidized via the routes of transamination and deamination. On the other hand, glutamate oxidation was initiated preferentially via transamination pathway in the tumor mitochondria. In the liver mitochondria, bicarbonate nearly at a physiological concentration inhibited oxygen uptake with glutamate as substrate. The interaction of bicarbonate with the pathway of glutamate oxidation occurred primarily at the level of succinate dehydrogenase, due to competitive inhibition of the enzyme by the compound. In contrast to the liver mitochondria, glutamate oxidation was not affected by bicarbonate in the tumor mitochondria. These results indicate that the aberrations in the glutamate metabolism and its regulation observed in the hepatoma mitochondria may be favorable to the respiration utilizing glutamine and/or glutamate as an energy source.
Department of Measles Virus, National Institute of Health, Tokyo, Japan.
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Matsuno
D000410:Alanine Transaminase / Q000378:metabolism; D000625:Aminooxyacetic Acid / Q000494:pharmacology; D001219:Aspartate Aminotransferases / Q000378:metabolism; D001639:Bicarbonates / Q000494:pharmacology; D006528:Carcinoma, Hepatocellular / Q000378:metabolism*; D005969:Glutamate Dehydrogenase / Q000378:metabolism; D005971:Glutamates / Q000378:metabolism*; D018698:Glutamic Acid; D005973:Glutamine / Q000378:metabolism; D006801:Humans; D008113:Liver Neoplasms / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism*; D008930:Mitochondria, Liver / Q000378:metabolism; D010084:Oxidation-Reduction; D010101:Oxygen Consumption / Q000187:drug effects; D013386:Succinates / Q000378:metabolism; D019802:Succinic Acid; D014407:Tumor Cells, Cultured
D001639:Bicarbonates; D005971:Glutamates; D013386:Succinates; D005973:Glutamine; D000625:Aminooxyacetic Acid; D018698:Glutamic Acid; D019802:Succinic Acid; D005969:Glutamate Dehydrogenase; D001219:Aspartate Aminotransferases; D000410:Alanine Transaminase