Enzymes-1

Enzymes-1

• Enzymes are proteins that act as catalysts, increasing the rate of chemical reactions. A literal definition relates them to yeast.
• Enzymes are proteins, and some are ribonucleic acids.
• Enzymes are highly efficient, producing 10³ to 10⁸ products per second and operating at 37°C. They are not consumed or changed during a chemical reaction.
• Enzymes exhibit specificity.
  • Substrate specificity: enzymes only attach to one particular substrate (e.g., urease for urea). If the substrate is an isomer (D or L), the enzyme only works on one isomer.
  • Group specificity: enzymes target groups of similar compounds (e.g., L-amino acid oxidase only attacks L-amino acids, not D-amino acids).
  • Low/relative specificity: enzymes bind to specific types of bonds (e.g. peptidase binds to peptide bonds in different peptide proteins).
  • Reaction specificity: enzymes catalyze specific pathways (e.g., glucose oxidase only catalyzes gluconic acid synthesis, not sorbitol synthesis).
• Most enzyme names end in "-ase".
• Active site (often a cleft): the substrate binding site of an enzyme.
• Substrate: the molecule on which an enzyme acts (e.g., starch for amylase, lipids for lipase).
• Holoenzyme (active enzyme) = Apoenzyme (protein part of the enzyme) + Coenzyme or cofactor (non-protein part of the enzyme).
• Not all enzymes require coenzymes. Coenzymes are complex, non-protein organic molecules that function as group transfer reagents and are categorized into two groups.
• Prosthetic group: a cofactor that binds strongly to an apoenzyme (e.g., heme in hemoglobin).
• Cofactors: cofactors weakly bind and easily dissociate from apenzymes (e.g., NAD in liver alcohol dehydrogenase).
• Not all enzymes are synthesized in their active form; some are synthesized as zymogens (e.g., pepsinogen, trypsinogen, and chymotrypsinogen).
• Most polar amino acids participate in catalysis within one or more enzymes.
• Enzyme-catalyzed reaction have three steps (Michaelis-Menten equation):
  • Binding of substrate: E + S <=> ES
  • Conversion of substrate to product: ES <=> EP
  • Release of product : EP → E + P
    • S = substrate; E= enzyme; ES= enzyme-substrate complex; P = product
    • k₁, k_-1, and k₂ are rate constants.
• The graph of substrate over time shows a decrease in substrate concentration with corresponding increase in product.
• Active enzyme = protein part + non-protein part
• Holo enzyme = (apoenzyme) + (cofactor)
• Protein part features an active site (like a pocket or cleft).
• Role of active site: substrate binding, determining enzyme specificity, and participating catalytically.
• E + S <=> ES <=> EP <=> E + P

Enzyme Nomenclature

• Trivial names: common names (e.g., pepsin, trypsin).
• Systematic names: include substrate name and "ase" (e.g., lipase, amylase, protease). This can also include type of reaction (e.g., lactate dehydrogenase).

This quiz delves into the fascinating world of enzymes, essential proteins that accelerate chemical reactions in living organisms. Covering definitions, types of specificity, and operational efficiency, it provides insights into their roles and mechanisms. Test your understanding of these biochemical catalysts and their unique properties.