The important properties of enzymes are listed below :– Chemical Nature:The enzymes are proteinic in nature. Some enzymes have additional non-protein (inorganic or organic) substances associated with them for their action. Molecular Weight:The enzymes have very high molecular weights. These vary from 6000 for bacterial ferredoxin to 4,600,000 for pyruvate dehydrogenase complex. Chemical Activity:The enzymes accelerate a chemical reaction by lowering activation energy. Changeless Form:The enzymes combine temporarily with the substrate molecules but are not consumed or changed permanently in the reaction they catalyse. They are produced in same form at the end of reaction. Reversibility of Reaction:The enzyme – controlled reactions are reversible. High Efficiency:Most enzymes have high turnover number. A molecule of the enzyme catalse from cattle liver decomposes 5,000,000 molecules of hydrogen peroxide to water and hydrogen in one minute at 0oC. The turnover number of carbonic anhydrase present in the RBCs is 36 million. The higher the turnover number, the more efficient is enzyme. Action Specificity:The enzymes are specific in action. Temperature Sensitivity:The enzymes function best at an optimum temperature. The optimum temperature for human enzymes is 35 to 40oC- close to human body temperature. The enzyme activity decreases as well as increase in temperature, and stops at 0oC and above 800C. the enzymes of bacteria inhabiting hot springs have an optimum temperature of 700C or more. pH Sensitivity:The enzymes show maximum activity at an optimum pH (6-8) but enzymes have specific pH for their action.