Pyruvate cycling
Encyclopedia
Pyruvate cycling commonly refers to an intracellular loop of spatial movements and chemical transformations involving pyruvate. Spatial movements occur between mitochondria
and cytosol
and chemical transformations create various Krebs cycle intermediates. In all variants, pyruvate is imported into the mitochnodrion for processing through part of the Krebb's cycle. In addition to pyruvate, alpha-ketoglutarate may also be imported. At various points, the intermediate product is exported to the cytosol for additional transformations and then re-imported. Three specific pyruvate cycles are generally considered, each named for the principal molecule exported from the mitochondrion: malate, citrate, and iso-citrate.Other variants may exist, such as dissipative or "futile" pyruvate cycles.
This cycle is usually studied in relation to Glucose Stimulated Insulin Secretion ( or GSIS ) and there is thought to be a relationship between the insulin response and NADPH produced from this cycle but the specifics are not clear and particular confusion exists about the role of malic enzymes.It has been observed in various cell types including islet cells.
The pyruvate-malate cycle was described in liver and kidney preparations as eary as 1971.
Mitochondrion
In cell biology, a mitochondrion is a membrane-enclosed organelle found in most eukaryotic cells. These organelles range from 0.5 to 1.0 micrometers in diameter...
and cytosol
Cytosol
The cytosol or intracellular fluid is the liquid found inside cells, that is separated into compartments by membranes. For example, the mitochondrial matrix separates the mitochondrion into compartments....
and chemical transformations create various Krebs cycle intermediates. In all variants, pyruvate is imported into the mitochnodrion for processing through part of the Krebb's cycle. In addition to pyruvate, alpha-ketoglutarate may also be imported. At various points, the intermediate product is exported to the cytosol for additional transformations and then re-imported. Three specific pyruvate cycles are generally considered, each named for the principal molecule exported from the mitochondrion: malate, citrate, and iso-citrate.Other variants may exist, such as dissipative or "futile" pyruvate cycles.
This cycle is usually studied in relation to Glucose Stimulated Insulin Secretion ( or GSIS ) and there is thought to be a relationship between the insulin response and NADPH produced from this cycle but the specifics are not clear and particular confusion exists about the role of malic enzymes.It has been observed in various cell types including islet cells.
The pyruvate-malate cycle was described in liver and kidney preparations as eary as 1971.