Sandbox 160: Difference between revisions

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== Structure & Function ==

Glyceraldehyde 3-Phosphate Dehydrogenase (GAPDH)has carefully been studied in a number of bacterial, parasitic and mammalian species and it has been found that it exists as homotetrameric protein <ref name="reference 1"/>. Each subunit within the protein contains seven alpha helices and two beta sheets in which ~~one contains~~ seven strands and the other ~~has~~ eight<ref name="reference 1"/>. Two anion binding sites have been found where the two phosphates involved in the reaction will be bound during catalysis. One site is labeled "Pi" and is the location where the inorganic phosphate involved will bind and the other has been labeled "Ps" which is where the C-3 phosphate of Gylceraldeyhde 3-Phosphate will bind <ref name="reference 1"/> . Further experimentation has shown that the "Ps" site has been conserved in numerous GAPDH complexes and that the former may involve two possible sites.

Glyceraldehyde 3-Phosphate Dehydrogenase (GAPDH)has carefully been studied in a number of bacterial, parasitic and mammalian species and it has been found that it exists as homotetrameric protein <ref name="reference 1"/>. Each subunit within the protein is 38,151Da (tetramer is 152.4 kDa)and contains seven alpha helices and two beta sheets one of which has seven strands and the other with eight<ref name="reference 1"/> <ref name="ref 5">PMID:15953771</ref>. Each monomer is 38,151Da Two anion binding sites have been found where the two phosphates involved in the reaction will be bound during catalysis. One site is labeled "Pi" and is the location where the inorganic phosphate involved will bind and the other has been labeled "Ps" which is where the C-3 phosphate of Gylceraldeyhde 3-Phosphate will bind <ref name="reference 1"/> . Further experimentation has shown that the "Ps" site has been conserved in numerous GAPDH complexes and that the former may involve two possible sites.

The enzyme contains a functional NAD+ group which functions as a hydrogen acceptor during the course of the reaction which is bound to a Rossman fold. During the catalysis of glyceraldehyde 3-phosphate to 1,3-biphosphoglycerate a hydride ion is enzymatically transferred from the aldehyde group of glyceraldehyde 3-phosphate to the nicotinamide ring of NAD+ reducing it to NADH (pink)<ref name="reference 1">PMID:19243605 </ref>. The active site of GAPDH contains a cysteine (Cys149 colored green) residue which reacts with the glyceraldehyde 3-phosphate molecule through its -SH group. The substrate is covalently bound during the reaction through its aldehyde group to the -SH group of the cysteine residue and the resulting reaction produces a thiohemiacetal intermediate <ref name="reference 1"/>. Note that this reaction occurs through acid base catalysis with aid of a histidine residue (His176).The <scene name='Sandbox_160/Newscene/1'>active site</scene> of the molecule is illustrated to the right.

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 == Structure & Function ==
-Glyceraldehyde 3-Phosphate Dehydrogenase (GAPDH)has carefully been studied in a number of bacterial, parasitic and mammalian species and it has been found that it exists as homotetrameric protein <ref name="reference 1"/>. Each subunit within the protein contains seven alpha helices and two beta sheets in which one contains seven strands and the other has eight<ref name="reference 1"/>. Two anion binding sites have been found where the two phosphates involved in the reaction will be bound during catalysis. One site is labeled "Pi" and is the location where the inorganic phosphate involved will bind and the other has been labeled "Ps" which is where the C-3 phosphate of Gylceraldeyhde 3-Phosphate will bind <ref name="reference 1"/> . Further experimentation has shown that the "Ps" site has been conserved in numerous GAPDH complexes and that the former may involve two possible sites.
+Glyceraldehyde 3-Phosphate Dehydrogenase (GAPDH)has carefully been studied in a number of bacterial, parasitic and mammalian species and it has been found that it exists as homotetrameric protein <ref name="reference 1"/>. Each subunit within the protein is 38,151Da (tetramer is 152.4 kDa)and contains seven alpha helices and two beta sheets one of which has seven strands and the other with eight<ref name="reference 1"/> <ref name="ref 5">PMID:15953771</ref>. Each monomer is 38,151Da   Two anion binding sites have been found where the two phosphates involved in the reaction will be bound during catalysis. One site is labeled "Pi" and is the location where the inorganic phosphate involved will bind and the other has been labeled "Ps" which is where the C-3 phosphate of Gylceraldeyhde 3-Phosphate will bind <ref name="reference 1"/> . Further experimentation has shown that the "Ps" site has been conserved in numerous GAPDH complexes and that the former may involve two possible sites.
 The enzyme contains a functional NAD+ group which functions as a hydrogen acceptor during the course of the reaction which is bound to a Rossman fold. During the catalysis of glyceraldehyde 3-phosphate to 1,3-biphosphoglycerate a hydride ion is enzymatically transferred from the aldehyde group of glyceraldehyde 3-phosphate to the nicotinamide ring of NAD+ reducing it to NADH (pink)<ref name="reference 1">PMID:19243605 </ref>. The active site of GAPDH contains a cysteine (Cys149 colored green) residue which reacts with the glyceraldehyde 3-phosphate molecule through its -SH group. The substrate is covalently bound during the reaction through its aldehyde group to the -SH group of the cysteine residue and the resulting reaction produces a thiohemiacetal intermediate <ref name="reference 1"/>. Note that this reaction occurs through acid base catalysis with aid of a histidine residue (His176).The <scene name='Sandbox_160/Newscene/1'>active site</scene> of the molecule is illustrated to the right.