Enzymes

• Enzymes - proteins which catalyze or speed up a chemical reaction.
• Active Site - a pocket/groove shaped to fit the substrate. It is a specific region in the enzyme where the substrate binds and catalysis occurs.
• Active Site - enables the enzyme to lower the activation energy required for a reaction which facilitates faster reactions.
• Active Site - determines the enzyme's specificity which means it can bind only certain substrates with a specific shape and chemical properties.
• Substrate Binding Site - has a complementary shape to the substrate. It is the part of the enzyme where the substrate temporarily binds.
• Substrate Binding Site - holds the substrate in place, positioning it correctly for the catalytic reaction. It ensures specificity as only compatible substrates can bind effectively.
• Catalyst - lowers the activation energy needed for a reaction to occur.
• Catalyst - speeds up the reaction but remains unchanged at the end of the reaction.
• Catalytic Site - contains key amino acids for catalysis. It is a part of the active site where the actual chemical reaction occurs. It contains residues directly involved in bond breaking and forming.
• Catalytic Site - stabilizes the transition state and provides the correct environment for the reaction to proceed effectively.
• Coenzyme/Cofactor Binding Site - is a specific pocket for cofactor attachment. It is a region in the enzyme where cofactors and coenzymes bind. They are typically near the active or catalytic site.
• Coenzymes/Cofactors Binding Site - this site helps secure coenzymes or cofactors which assists in catalysis by providing additional chemical groups, stabilizing intermediates, or facilitating electron transfer.
• Cofactors - carry out specific functions that amino acids alone cannot, broadening the enzymes' capabilities.
• Allosteric Site - site on an enzyme where molecules bind, causing shape changes that regulate enzyme activity. It allows enzymes to adapt to environmental changes, maintaining cellular balance. It is shaped for regulatory molecules rather than substrates.
• Levels of Organization in Protein Structures

  • primary
  • secondary
  • tertiary
  • quaternary
• Primary Structure - has a linear structure of amino acids, determining the protein's unique characteristics.
• Secondary Structure - folding into alpha-helices and beta-sheets which is stabilized by hydrogen bonds.
• Tertiary Structure - 3D shape formed by R group interactions, it defines active sites, and are stabilized by various bonds.
• Quaternary Structure - complex of multiple polypeptide chains forming a functional protein.
• Prosthetic Groups - are non-protein molecules tightly bound to enzymes which are essential for enzyme activity. They enable reactions that amino acids alone cannot, they often stabilize enzyme states or transfer electrons.
• Examples of Enzymes

  • hexokinase
  • ATCase (Aspartate Transcarbamoylase)
  • Cytochrome C Oxidase
  • LDH (Lactate Dehydrogenase)
• Hexokinase - is has a tertiary structure. It catalyzes glucose phosphorylation in glycolysis which traps glucose in cells for energy production.
• ATCase - it has a quaternary structure. It catalyzes pyrimidine nucleotide synthesis which are regulated by CTP and ATP for DNA/RNA balance.
• Cytochrome C Oxidase - has a quaternary structure. It is the final enzyme in the electron transport chain, it reduces oxygen to water which is critical for ATP production.
• Lactate Dehydrogenase - has a quaternary structure. It converts pyruvate to lactate in anaerobic conditions, regenerating NAD+ to sustain glycolysis in low-oxygen settings.
• Lock and Key - displays a foxed structure for the enzyme and substrate therefore no adjustment happens when they combine.
• Induced Fit - both the enzyme and the substrate adjusts slightly to fit with each other when they bind.