Y1S2 003 I Biochem First Amino Acid in a Protein Sequence

Thermolysin and Proteins

• Thermolysin is a thermostable zinc endopeptidase that contains a zinc ion for catalysis and four calcium ions for thermal stability.
• It cleaves peptides at amino-linked bonds of aliphatic amino acids (e.g., Val, Ile, Leu) that resist heat.
• The proposed mechanism for thermolysin-catalyzed cleavage of peptides involves the cleavage of amino-linked bonds of aliphatic amino acids.

Enzyme Function and Specificity

• Enzymes are highly specialized and have specific purposes in the body.
• Enzymes are composed of amino acids linked together.
• Enzymes increase reaction rates by decreasing the activation energy.
• Enzymes have varying degrees of specificity for substrates, recognizing and catalyzing a single substrate, a group of similar substrates, or a particular type of bond.

Mechanism of Action of Enzymes

• Enzymes increase reaction rates by decreasing the activation energy.
• Enzyme-substrate interactions involve the formation of an enzyme-substrate complex through the lock-and-key model or the induced-fit model.
• The lock-and-key model describes the active site as having a rigid shape that only allows substrates with the matching shape to fit.
• The induced-fit model describes the active site as flexible, adjusting to maximize the fit with the substrate.

Factors Affecting Enzyme Activity

• Environmental conditions, such as temperature, pH, and substrate concentration, affect enzyme activity.
• Optimum temperature, pH, and substrate concentration vary for different enzymes.
• Cofactors and coenzymes, such as inorganic substances and vitamins, are sometimes necessary for proper enzymatic activity.

Enzyme Inhibitors

• Enzyme inhibitors slow down the reaction rate by binding to the active site, reducing the enzyme's activity.
• Competitive inhibitors resemble the substrate and bind to the active site, reducing the enzyme's activity.
• Non-competitive inhibitors bind to a different location on the enzyme, causing a conformational change that slows down the reaction rate.