Explain5 marksChallenge
A novel enzyme, Xylanase-4, is found in a soil bacterium and catalyses the hydrolysis of xylan, a polysaccharide found in plant cell walls. The enzyme does not catalyse the hydrolysis of cellulose, starch, or other polysaccharides. Studies show that when the active site of Xylanase-4 is compared to that of a closely related enzyme that hydrolyses cellulose, the shapes and chemical properties differ. Additionally, when Xylanase-4 binds to xylan, the active site undergoes a slight conformational change that tightens around the substrate. Explain why Xylanase-4 is specific for xylan. In your answer, refer to the lock-and-key and induced-fit models of enzyme action and describe how enzymes lower activation energy.