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.
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[edit] Reaction
In this shuttle, the enzyme called cytoplasmic glycerol-3-phosphate dehydrogenase (GPD) converts dihydroxyacetone phosphate (2) to glycerol 3-phosphate (1) by oxidizing one molecule of NADH to NAD+ as in the following reaction:[1]
[edit] Reverse path
Glycerol-3-phosphate gets converted back to dihydroxyacetone phosphate by a membrane-bound mitochondrial glycerol-3-phosphate oxidase, 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 phosphorylation.[1] This reaction is irreversible.[2]
[edit] Function
The glycerol-3-phosphate shuttle allows the NADH synthesized in the cytosol by glycolysis to contribute to the oxidative phosphorylation pathway in the mitochondria to generate ATP.[1] It has been found in animals, fungi, and plants.[2]
[edit] See also
[edit] References
- ^ a b c Stryer, Lubert; Berg, Jeremy Mark; Tymoczko, John L. (2007). Biochemistry. San Francisco: W. H. Freeman. ISBN 0-7167-8724-5. http://bcs.whfreeman.com/biochem6/default.asp?s=&n=&i=&v=&o=&ns=0&uid=0&rau=0.
- ^ a b Shen W, Wei Y, Dauk M, et al. (February 2006). "Involvement of a glycerol-3-phosphate dehydrogenase in modulating the NADH/NAD+ ratio provides evidence of a mitochondrial glycerol-3-phosphate shuttle in Arabidopsis". Plant Cell 18 (2): 422β41. doi:10.1105/tpc.105.039750. PMC 1356549. PMID 16415206. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1356549.
[edit] External links
- http://www.elmhurst.edu/~chm/vchembook/601glycolysissum.html (describes the shuttle in the context of glycolysis)
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