Question

Describe the reaction of gluconeogenesis and for each step explain the type of reaction, enzyme involved, substrate and product, if the reaction is reversible or irreversible, any coenzyme or prosthetic group involved, and location.

Answer 1

Figure 1

Synthesis of glucose is known as gluconeogenesis. In figure 1. step 1 takes place in mitochondria. Step 2 can take place either in mitochondria and cytosol as enzyme PEPCK is present in both compartments. The location of PEPCK is differ from species to species. In rat liver and mouse, PEPCK express in the cytosol, in rabbit and pigeon liver it is mitochondrial, and in humans and guinea pig it is located in both compartments. Step 3 to 10 exclusively takes place in the cytosol. Enzymes involved, substrate, prostatic groups, product of each steps has been mentioned in the figure.

Figure 2

It is called glyoxylate cycle. This is another pathway which leads to formation of gluconeogenesis. Step 1. aconitase is the cytosolic enzyme. While all other enzymes of reaction 2 to 5 are present in glyoxysome. Step 6 and 7 takes place in mitochondria. Step 8 and 9 take place in cytosol. from step 9 onwards please follow figure 1. Enzymes involved, substrate, prostatic groups, product of each steps has been mentioned in the figure.