Enzymes in Metabolic Pathways

Enzymes in Metabolic Pathways

• Enzymes are proteins that speed up metabolic chemical reactions, allowing cells to stay alive and function properly.
• Enzymes lower the energy needed for a reaction to start, making the reaction faster.

Enzyme-Substrate Binding

• Enzymes bind to substrates by changing their shape to fit the substrates better and stabilize them during the reaction.

Regulation of Enzymes

• Allosteric regulation: molecules bind to a different site on the enzyme, changing its activity (e.g., ATP inhibits PFK-1 in glycolysis).
• Covalent modification: adding or removing groups like phosphate activates or deactivates enzymes.
• Proteolytic cleavage: enzymes are activated by cutting (e.g., trypsinogen is cut to form active trypsin).
• Feedback inhibition: end products inhibit earlier steps in the pathways (e.g., isoleucine inhibits threonine deaminase).
• Compartmentalization: enzymes are kept in specific cell areas (e.g., fatty acid synthesis occurs in the cytoplasm, while breakdown occurs in mitochondria).

Importance of Enzymes

• Enzymes help maintain balance in the cell by controlling metabolic reactions and responding to changes.
• Enzymes regulate blood sugar levels (e.g., insulin and glucagon regulate enzymes that control blood sugar levels).
• The role of enzymes is crucial for speeding up and regulating metabolic reactions, ensuring cells function properly and stay balanced.