Glycerol phosphate shuttle

Glycerol phosphate shuttle

The glycerol-3-phosphate shuttle is a mechanism that regenerates NAD+ from NADH, a by-product of glycolysis. Its importance in transporting reducing equivalents is secondary to the malate-aspartate shuttle.

Reaction

In this shuttle, the enzyme called cytoplasmic glycerol-3-phosphate dehydrogenase converts dihydroxyacetone phosphate to glycerol 3-phosphate by oxidizing one molecule of NADH to NAD+ as in the following reaction:



Reverse path

Glycerol-3-phosphate gets converted back to dihydroxyacetone phosphate by a membrane-bound mitochondrial glycerophosphate dehydrogenase, this time reducing one molecule of enzyme-bound flavin adenine dinucleotide (FAD) to FADH2. FADH2 then reduces coenzyme Q (ubiquinone to ubiquinol) which enters into oxidative phosphorylization. This reaction is irreversible.cite journal |author=Shen W, Wei Y, Dauk M, "et al" |title=Involvement of a glycerol-3-phosphate dehydrogenase in modulating the NADH/NAD+ ratio provides evidence of a mitochondrial glycerol-3-phosphate shuttle in Arabidopsis |journal=Plant Cell |volume=18 |issue=2 |pages=422–41 |year=2006 |month=February |pmid=16415206 |pmc=1356549 |doi=10.1105/tpc.105.039750]

Function

The glycerol-3-phosphate shuttle allows the NADH synthesized in the cytosol by glycolysis to contribute to the oxidative phosphorylization pathway in the mitochondria to generate ATP.cite book |author=Stryer, Lubert; Berg, Jeremy Mark; Tymoczko, John L. |title=Biochemistry |publisher=W. H. Freeman |location=San Francisco |year=2007 |pages= |isbn=0-7167-8724-5 |oclc= |doi= |url=http://bcs.whfreeman.com/biochem6/default.asp?s=&n=&i=&v=&o=&ns=0&uid=0&rau=0] It has been found in animal, fungus, and plant.

ee also

* Malate-aspartate shuttle
* Mitochondrial shuttle

References

External links

* http://www.elmhurst.edu/~chm/vchembook/601glycolysissum.html (describes the shuttle in the context of glykolysis)
* http://courses.cm.utexas.edu/jrobertus/ch339k/overheads-3/ch19_glycerol-shuttle.jpg (illustration of the two reactions)


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