Thursday, September 20, 2012
• Large proteins that catalyze chemical reactions in cells
• They are very specific, and do not get consumed in the reaction
• Have an "active site" which is an area to which the substrate binds
• The precise atomic arrangement in/of the active site is needed for this interaction which
recognizes a specific substrate
Within a split second of binding, the substrate is converted to product and the enzyme
molecule can bind the next substrate molecule
Mechanisms of Enzyme Action
• Enzymes are said to lower the activation energy for the reaction.
• What does this mean?
• How can an enzyme lower the activation energy?
Two basic mechanisms:
• Juxtaposition of substrate molecules
• Inducing stress in the substrate- physical stress, i.e hydrolyze sucrose a bond
needs to be broken, substrate binds to enzyme, enzyme pulls on covalent bond so it
• With enzyme lower activation energy
Non-Protein Portions of Enzymes
• Called co-factors in enzyme action- located somewhere near the active site
• Most commonly these are vitamins or minerals that are part of our nutritional
• These cofactors often participate in the catalytic process and are essential for the
biological activity of the enzyme Regulation of Enzyme Activity