Format

Send to:

Choose Destination
See comment in PubMed Commons below
Am J Physiol Endocrinol Metab. 2001 Dec;281(6):E1300-7.

Threonine metabolism in isolated rat hepatocytes.

Author information

  • 1Department of Biochemistry, Memorial University of Newfoundland, St. John's, Newfoundland, A1B 3X9, Canada.

Abstract

The removal of the 1-carbon of threonine can occur via threonine dehydrogenase or threonine aldolase, this carbon ending up in glycine to be liberated by the mitochondrial glycine cleavage system and producing CO(2). Alternatively, in the threonine dehydratase pathway, the 1-carbon ends up in alpha-ketobutyrate, which is oxidized in the mitochondria to CO(2). Rat hepatocytes, incubated in Krebs-Henseleit medium, were incubated with 0.5 mM L-[1-(14)C]threonine, and (14)CO(2) production was measured. Added glycine (0.3 mM) marginally suppressed threonine oxidation. Cysteamine (0.5 mM), a potent inhibitor of the glycine cleavage system, reduced threonine oxidation to 65% of controls. However, alpha-cyanocinnamate (0.5 mM), a competitive inhibitor of mitochondrial alpha-keto acid uptake, reduced threonine oxidation to 35% of controls. These data provided strong evidence that approximately 65% of threonine oxidation occurs through the glycine-independent threonine dehydratase pathway. Glucagon (10(-7) M) increased threonine oxidation and stimulated threonine uptake by these cells. In summary, the majority of threonine oxidation occurs through the threonine dehydratase pathway in rat hepatocytes, and threonine oxidation is increased by glucagon, which also increases threonine's transport.

PMID:
11701446
[PubMed - indexed for MEDLINE]
Free full text
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for HighWire
    Loading ...
    Write to the Help Desk