Question

Which cofactor is most important in metabolic (catabolic) pathways? Rationalize your answer and discuss what pathways can it be regenerated.

Answer 1

The most important cofactor in metabolic(catabolic) pathways is Magnesium (Mg 2+).

Mg2+ is very important for the enzymes involved in the Glycolytic Pathway, TCA cycle. Glycolysis and TCA cycle are the most important pathways involved in ATP synthesis. Both pathways are involved in all eukaryotes.

Mg2+ is important for enzymes like Hexokinase, Phosphohexose isomerase, Phosphofructokinase 1, Phosphoglycerate kinase, Phosphoglycerate mutase, Pyruvate Kinase. All of these enzymes are involved in Glycolysis.

Hexokinase converts Glucose to Glucose-6-phosphate, Phosphohexose isomerase converts Glucose-6-phosphate to Fructose 6-Phosphate, Phosphofructokinase 1 converts Fructose 6-Phosphate to Fructose 1,6-Bisphosphate, Phosphoglycerate kinase transfers high-energy phosphoryl group from the carboxyl group of 1,3-BPG to ADP, forming ATP & 3-phosphoglycerate (3PG), Phosphoglycerate mutase converts 3-Phosphoglycerate to 2-Phosphoglycerate, Pyruvate Kinase converts Phosphoenolpyruvate to Pyruvate.

Mg2+ is also involved in the formation of Acetyl CoA from Pyruvate. It helps Pyruvate dehydrogenase as a cofactor.

Mg2+ also helps enzymes like isocitrate dehydrogenase (IDH) and 2-oxoglutarate dehydrogenase complex (OGDH) involved in the TCA cycle, as a cofactor. IDH catalyzes the oxidation of Isocitrate to α-Ketoglutarate & CO2.OGDH catalyzes the oxidation of α-Ketoglutarate to Succinyl-CoA & CO2.

So, it is clear that Mg2+ is the most important cofactor in catabolic pathways.