What is the function of glyceraldehyde 3-phosphate dehydrogenase?

Question

BlackTom AI · Accepted Answer

Let’s examine what glyceraldehyde 3-phosphate dehydrogenase (GAPDH) actually does in metabolism. 
Option 1: 'oxidation of an aldehyde by NAD+ and formation of acyl-phosphate' correctly describes GAPDH activity. It oxidizes the aldehyde group of glyceraldehyde-3-phosphate and transfers the electrons to NAD+, forming NADH, while the inorganic phosphate is added to create the high-energy acyl-phosphate (1,3-bisphosphoglycerate). This is the canonical reaction in glycolysis and links the oxidation step to energy capture. 
Option 2: 'oxidation of an alcohol to an aldehyde by NAD+' is not correct here, because GAPDH acts on an aldehyde, not on an alcohol, and it oxidizes to a carboxylic acid derivative (as part of forming a phosphate acyl intermediate), not simply converting an alcohol to an aldehyde. 
Option 3: 'dehydration and dephosphorylation of GAP' describes a removal of water and phosphate, which GAPDH does not perform; dehydration/dephosphorylation would be characteristic of other enzyme activities (e.g., certain kinases or lyases) but not GAPDH’s function in glycolysis. 
Option 4: 'hydrolysis of GAP' would mean breaking GAP apart with water, which GAPDH does not do; hydrolysis would yield separate fragments rather than forming the high-energy acyl-phosphate intermediate. 
Option 5: 'removal of the 3-phosphoryl-group from GAP' would descriptively indicate dephosphorylation of GAP itself, but GAPDH does not remove the 3-phosphate from GAP; instead, NAD+-dependent oxidation occurs with phosphate incorporation into the product as part of 1,3-bisphosphoglycerate formation. 
In summary, option 1 accurately captures the dual redox and phosphoryl-transfer nature of GAPDH’s role, while the other options misstate the substrate, reaction type, or products involved.

What is the function of glyceraldehyde 3-phosphate dehydrogenase?Single choice

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