Answer
Sucrase can catalyse the hydrolytic break down of sucrose into the sugars fructose and glucose. But sucrase cannot catalyze the fehydraton synthesis of the product sucrose from reactants glucose and fructose; in other words , this is not a reversible reaction. The inability of sucrase to catalyze the synthesis of sucrose may be due to a combination of factors:
1. The law of mass action. The products of hydrolysis may be used up so quickly that do not have time to accumulate and shift the reaction to the left according to the requirements of the law of mass action.
2.. Too much energy may be adsorbed by the product so that not enough is left to activate the reverse reaction.
3. Enzyme-reactants fit is essential for enzyme action. This may be missing in this connection--that is, the synthesis of sucrose from glucose and fructose by sucrase.
Work Step by Step
The synthesis of sucrose takes place mainly in plants but the details of the process is not completely understood.. According to current understanding, sucrose is synthesized from the substrates UDP-glucose and fructose-6-phosphate. The reaction is catalyzed by the enzyme sucrose-6-phosphate synthase, and the energy fort he reaction is obtained by cleaving the UDP from UDP-glucose. This reaction takes place in plants, but sucrose has been also synthesized chemically in laboratories.
