The glycerol-3-phosphate shuttle
is a mechanism that regenerates NAD+ from NADH, a by-product of glycolysis
. 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.
NADH + H+
Glycerol-3-phosphate then gets converted back to dihydroxyacetone posphate by a membrane-bound mitochondrial glyceraldehyde-3-phosphate dehydrogenase, this time reducing one molecule of enzyme-bound flavin adenine dinucleotide (FAD) to FADH2
then reduces coenzyme Q (Ubiquinin to Ubiquinone) which enters into oxidative phosphorylization.
The glycerol-3-phosphate shuttle allows the NADH to contribute to the oxidative phosphorylization pathway in the mitochondria to generate ATP.
Jeremy M. Berg, Tymoczko, and Stryer. "Biochemistry." 6th ed. W.H. Freeman and Company, New York: 2007