Alpha-Keto Acid Dehydrogenase Complexes and Glycine Cleavage System

2008 ◽  
Author(s):  
Robert Harris ◽  
Nam Ho Jeoung ◽  
Byounghoon Hwang ◽  
Mandar Joshi
Keyword(s):  
Keto Acid ◽  
Glycine Cleavage System ◽  
Acid Dehydrogenase ◽  
Glycine Cleavage

Threonine metabolism in isolated rat hepatocytes

2001 ◽  
Vol 281 (6) ◽  
pp. E1300-E1307 ◽  
Author(s):  
James D. House ◽  
Beatrice N. Hall ◽  
John T. Brosnan
Keyword(s):  
Potent Inhibitor ◽  
Rat Hepatocytes ◽  
Competitive Inhibitor ◽  
Acid Uptake ◽  
Keto Acid ◽  
Glycine Cleavage System ◽  
Isolated Rat Hepatocytes ◽  
Threonine Dehydratase ◽  
Threonine Dehydrogenase ◽  
Glycine Cleavage

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 CO2. Alternatively, in the threonine dehydratase pathway, the 1-carbon ends up in α-ketobutyrate, which is oxidized in the mitochondria to CO2. Rat hepatocytes, incubated in Krebs-Henseleit medium, were incubated with 0.5 mMl-[1-14C]threonine, and14CO2 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, α-cyanocinnamate (0.5 mM), a competitive inhibitor of mitochondrial α-keto acid uptake, reduced threonine oxidation to 35% of controls. These data provided strong evidence that ∼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.

scholarly journals α-Keto Acid Dehydrogenase Complexes

1973 ◽  
Vol 248 (24) ◽  
pp. 8348-8352 ◽  
Author(s):  
C. Stanley Tsai ◽  
Michael W. Burgett ◽  
Lester J. Reed
Keyword(s):  
Keto Acid ◽  
Acid Dehydrogenase
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