Pyruvate cycling commonly refers to an intracellular loop of spatial movements and chemical transformations involving
pyruvate
Pyruvic acid (CH3COCOOH) is the simplest of the alpha-keto acids, with a carboxylic acid and a ketone functional group. Pyruvate, the conjugate base, CH3COCOO−, is an intermediate in several metabolic pathways throughout the cell.
Pyruvic aci ...
. Spatial movements occur between
mitochondria and
cytosol
The cytosol, also known as cytoplasmic matrix or groundplasm, is one of the liquids found inside cells ( intracellular fluid (ICF)). It is separated into compartments by membranes. For example, the mitochondrial matrix separates the mitochondri ...
and chemical transformations create various
Krebs cycle
The citric acid cycle (CAC)—also known as the Krebs cycle or the TCA cycle (tricarboxylic acid cycle)—is a series of chemical reactions to release stored energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and protein ...
intermediates. In all variants, pyruvate is imported into the mitochondrion for processing through part of the Krebs 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 isocitrate. 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 early as 1971.
References
Further reading
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External links
* from {{cite journal , doi=10.1038/nrm2327 , pmid=18200017 , title=Mechanisms of disease: Molecular and metabolic mechanisms of insulin resistance and β-cell failure in type 2 diabetes , year=2008 , last1=Muoio , first1=Deborah M. , last2=Newgard , first2=Christopher B. , journal=Nature Reviews Molecular Cell Biology , volume=9 , issue=3 , pages=193–205, s2cid=3335727
Metabolism