What factors affect the rate of enzyme-mediated reactions?

Enzymes are a group of proteins that catalyze chemical reactions without undergoing any change themselves. 

These are the main factors that enhance or suppress an enzyme’s activity, affecting the rate of enzyme-mediated reactions: 

• Enzyme concentration - Increasing enzyme concentration increases the rate of the enzyme-mediated reaction provided there is a sufficient concentration of substrate available. This is because at higher enzyme concentrations, more enzyme molecules are available to process the substrate. At constant substrate concentration, the concentration of enzymes is the limiting factor. 
• Substrate concentration - Increasing substrate concentration increases the rate of the enzyme-mediated reaction provided there is a sufficient concentration of enzyme available. This is because at higher substrate concentrations, more substrate molecules are available to bind to the enzyme. At constant enzyme concentration, the concentration of substrate is the limiting factor because the enzymes become saturated with substrate and cannot process any more. 
• Temperature - Every enzyme has an optimum temperature at which it works most efficiently. Increasing the temperature generally increases enzyme activity because the higher temperature increases molecular motion resulting in more molecular collisions. The higher the number of molecular collisions, the faster the reaction rate. However, when the temperature reaches a certain point, the reaction rate slows down. This is because the high heat breaks the enzyme’s hydrogen bonds, denaturing the enzyme and causing it to lose its functional shape. Very low temperatures also decrease the reaction rate because molecular action slows down at low temperatures. 
• pH - Every enzyme has an optimal pH range within which it maintains its three-dimensional shape and is most active. pH values that fall outside of the optimal range alters the ionic bonds that contribute to the enzyme’s functional shape. This alters the enzyme’s charge and denatures the enzyme, affecting the rate of the reaction. 
• Presence of effector or inhibitor - The presence of effectors such as cofactors or metal ions helps to establish the enzyme’s catalytic function, increasing the rate of the reaction. The presence of inhibitors helps to inhibit the enzyme’s ongoing catalytic activity, preventing successive catalytic events, slowing down the rate of the reaction.