Which Enzyme is NOT Involved in the First 5 Steps

Question

Which enzyme is NOT involved in the first 5 steps of glycolysis?
A)phosphofructokinase-1 (PFK-1)
B)phosphoglycerate kinase
C)fructose bisphosphate aldolase
D)triose phosphate isomerase (TPI)

Accepted Answer

The first 5 steps of glycolysis include the conversion of glucose to fructose-6-phosphate, the conversion of fructose-6-phosphate to glyceraldehyde-3-phosphate and dihydroxyacetone phosphate (catalyzed by aldolase), the conversion of dihydroxyacetone phosphate to glyceraldehyde-3-phosphate (catalyzed by TPI), and the conversion of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate (catalyzed by glyceraldehyde-3-phosphate dehydrogenase). Phosphoglycerate kinase catalyzes the conversion of 1,3-bisphosphoglycerate to 3-phosphoglycerate in step 6 of glycolysis. Therefore, it is not involved in the first 5 steps.