Converts glyceraldehyde-3-phosphate (G3P) into 1,3-Bisphospho-D-glycerate (BPG). This is a vital step in glycolysis (as are all the steps) but the enzyme has some other activities. These include binding viral RNA which sometimes inhibits and sometimes promotes viral growth. Product:

[C@2H]([OH])([C@2H2][O][P@2](=[O])([O-])[O-])[C](=[O])[O][P@2](=[O])([O-])[O-]

The mechanism:

                     O
                     | 
R-C=O -Cys-SH-> R-C-S-Cys (a thiohemiacetal) -NAD-> R-C=O
  |                  |                                      |
  H                  H                      (thioester) Cys-S
The cys is then deacetylated by a phosphate. In ALDH, the same mechanism occurs, but the deacetylation step uses a water molecule to hydrolyse.
As a classic glycolytic enzyme, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is an old beast. In the light of moonlighting enzymes, enzymes that seem to serve multiple functions in the cell, GAPDH has become the focus of research in fields of biology unrelated to metabolic biochemistry. Here are some of the other biochemical functions of this amazing enzyme:

As a result of these multiple biochemical activities, GAPDH has been implicated in biolgical processes including endocytosis, microtubule bundling, translational regulation, nuclear RNA export, phosphotransferase functions, DNA replication, DNA repair, nitric oxide metabolism, apoptosis, neuronal disorders, viral pathogenesis and prostate cancer. Much still needs to be done to elucidate these multiple functions. Numerous other enzymes also function in multiple ways, giving robustness and diversity to biological systems.



References

  • Sirover MA. New insights into an old protein: the functional diversity of mammalian glyceraldehyde-3-phosphate dehydrogenase. Biochimica et Biophysica Acta v 1432 (1999) p 159-184
  • Meyer-Siegler et al. A human nuclear uracil DNA glycosylase is the 37-kDa subunit of glyceraldehyde-3-phosphate dehydrogenase. Proceedings of the National Academy of Sciences v 88 (1991) pp 8460-8464

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