Regulation of Gluconeogenesis in the Guinea Pig Liver
Because of differences in the pattern of enzyme activities involved in glycolysis and gluconeo‐genesis between rat and guinea pig liver, the regulation of gluconeogenesis in guinea pig liver was studied. The following results were obtained: Starvation increases the capacity for gluconeogenesis from...
| Published in: | European Journal of Biochemistry |
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| Main Authors: | , , , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Wiley
1970
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| Subjects: | |
| Online Access: | http://dx.doi.org/10.1111/j.1432-1033.1970.tb01084.x https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1432-1033.1970.tb01084.x https://febs.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1432-1033.1970.tb01084.x |
| Summary: | Because of differences in the pattern of enzyme activities involved in glycolysis and gluconeo‐genesis between rat and guinea pig liver, the regulation of gluconeogenesis in guinea pig liver was studied. The following results were obtained: Starvation increases the capacity for gluconeogenesis from pyruvate in vivo . Gluconeogenesis from l ‐lactate and from pyruvate in isolated perfused livers is greater in the guinea pig than in the rat, whereas gluconeogenesis from other precursors is similar in both species. Long chain and medium chain fatty acids inhibit gluconeogenesis from l ‐lactate in isolated perfused rat liver. In the guinea pig liver the difference does not result from a lower rate of fatty acid oxidation but from a greater reduction in the cytoplasmic NAD + /NADH system. During enhanced fatty acid oxidation in guinea pig liver and in rat liver, similar changes in the concentrations of both acetyl‐ S ‐CoA and CoA‐SH are observed. With high concentrations of pyruvate as the gluconeogenic precursor, both fatty acids and ethanol lead to a slight stimulation of glucose formation by supplying hydrogen equivalents to the cytosolic NAD + /NADH system. Both glucagon and dibutyryl‐Ado‐3′:5′‐ P stimulate ureogenesis and ketogenesis in isolated perfused guinea pig liver. However, the stimulation of gluconeogenesis by glucagon and Ado‐3′:5′‐ P normally observed in isolated perfused rat livers was not found in isolated perfused guinea pig livers. Partially purified pyruvate carboxylases from rat and guinea pig liver do not differ with respect to the apparent K m values for pyruvate and ATP, and also the apparent K a values for acetyl‐ S ‐CoA at different pH values. At constant concentrations of MgATP 2− or MnATP 2− the pH‐optima for the guinea pig enzyme are significantly lower. 5‐Methoxyindole‐2‐carbonic acid inhibits gluconeogenesis in guinea pig liver in the same way as in rat liver. Quinolinate, on the other hand is far less inhibitory in guinea pig liver and does not inhibit at all in isolated perfused pigeon ... |
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