Biochemistry Nomenclature Committee Overview

Enzymes

• Enzymes are powerful biological catalysts.
• Rate accelerations by enzymes are significantly greater than those by synthetic or inorganic catalysts.
• Enzymes increase reaction rates, reducing activation barriers.
• Enzymes do not affect the equilibrium of reactions.
• Enzymes exhibit a very high degree of specificity.
• A single enzyme usually catalyzes only one chemical reaction, or occasionally a few closely related reactions.
• Enzymatic reactions take place in specialized pockets known as active sites.
• The conversion of a substrate to a product by an enzyme occurs within a specific active site.

Catalytic Power of Enzymes

• Enzymes bind most strongly to the transition state of the catalyzed reaction.
• This strong binding utilizes binding energy to lower the activation barrier.
• Enzyme active sites are evolved to enable multiple mechanisms of chemical catalysis simultaneously.

Enzyme Regulation

• Many enzymes are regulated.
• Enzymes are subject to multiple regulatory mechanisms, which provide precise control over each cellular chemical process.

Important Traits of Enzymes

• Enzymes are proteins.
• Enzymes are catalysts.
• Enzymes exhibit selectivity towards substrates.

Best Source of Enzymes

• Microorganisms are the best source of enzymes.
• Characteristics of beneficial microorganisms for enzyme production include high versatility, high production capacity, ease of genetic modification, and easy extraction of enzymes.
• Microorganisms to be used should not be pathogenic, be non-toxigenic, and not produce antibiotic substances.

Advantages of Enzymes Over Inorganic Catalysts

• Enzymes are natural and non-toxic.
• Products formed using enzymes are non-toxic.
• Enzymes are highly substrate or reaction-specific.
• Enzymes operate optimally under mild temperatures and pH conditions.
• Enzyme reaction rates are controllable.
• Enzyme activity is easily inactivated.

Uses of Enzymes in the Food Industry

• Improve processing techniques and improve product quality.
• Develop new flavors.
• Improve extraction techniques.
• Utilize by-products.

Structure of Enzymes

• Holoenzyme: A complete, catalytically active enzyme complex comprised of an apoenzyme and its associated coenzymes and/or metal ions.
• Apoenzyme/Apoprotein: The protein portion of an enzyme.
• Cofactor: An additional chemical component; it can be an inorganic ion like Fe²⁺, Mg²⁺, Mn²⁺, or Zn²⁺.
• Coenzyme: A complex organic or metalloorganic molecule derived from vitamins and/or organic nutrients.

Isoenzymes/Isoforms

• Multiple forms of enzymes exhibiting minor primary structure differences.
• These enzymes possess near-identical catalytic functionality.
• Enzymes catalyzing the same group of substances or the same reaction collectively belong to a specific class of isoenzymes.

Zymogens

• Enzymes are synthesized as inactive precursors, called zymogens.
• Proteolytic processing is needed to activate zymogens.

Nomenclature and Classification of Enzymes

• Seven enzyme classes exist, subdivided further into subclasses based on the catalyzed reaction type.
• Every enzyme is assigned a numerical classification number, alongside a systematic name.
• The Enzyme Commission Number (EC Number) is a numerical classification scheme based on the chemical reactions catalyzed by the enzyme.

Classification of Food Enzymes

• Exogenous Enzymes: Enzymes are added to food to cause desirable changes.
• Endogenous Enzymes: Enzymes present in foods, impacting food quality either positively or negatively.

Examples of Endogenous Enzymes

• Pectic Enzymes: Activity depends on the extent of methyl esterification of pectin.
  • Pectin lyases or pectin transeliminases split glycosidic bonds adjacent to a methyl ester via a β-elimination reaction.
  • Pectate lyases cleave glycosidic bonds adjacent to a free carboxyl group.
• Amylases: Responsible for starch hydrolysis.
  • α-amylase hydrolyzes starch randomly, reducing viscosity and increasing reducing power.
  • β-amylase acts on the reducing end of starch, leading to increased solution sweetness.
• Lipases: Hydrolyze ester linkages in triacylglycerols (glycerides).
  • Their activity affects desirable and undesirable flavors in foods resulting from hydrolyzed fatty acids.
• Browning Enzymes (Phenolase, Cresolase, Catecholase): These enzymes lead to enzymatic browning.
  • Convert phenolic compounds to orthoquinones, leading to melanin (brown pigment) formation.
• Lipoxigenases: Act on the cis, cis-1,4-pentadienes in lipid systems producing hydroperoxides.
  • These enzymes cause off-flavors in foods like soybeans.
• Peroxidases: Contain heme prosthetic group oxidizing ferric to higher valence states.
  • Results in carotenoid bleaching, Vitamin C destruction, and fatty acid peroxidation.
• Ascorbic Acid Oxidase: Copper-containing enzyme catalyzing the oxidation of ascorbic acid.

How Enzymes Work

• Enzymes speed up reaction rates without altering reaction equilibrium.
• The function of a catalyst is to increase rate.
• The ground state is the starting point for a forward or reverse reaction.
  • A favorable equilibrium doesn't guarantee a fast reaction rate; there's an energy barrier between starting material and product that needs to be overcome.
• Transition State: The highest energy state along the reaction coordinate represents the point when decay to substrate or product is equal.
• Enzymes bind to a transition state, not the ground state. Activation energies (energy needed for reaction) are lower for enzyme-catalyzed reactions.
• Binding Energy: Non-covalent interactions between enzyme and substrate release a small amount of energy. This energy lowers activation energy.
• Catalytic Power: Covalent interactions between the enzyme and substrate provide an alternative, lower-energy path.
• Functional groups form temporary covalent bonds with substrates to activate them.
  • Functional groups can be transferred from substrates to enzymes.

Enzyme Kinetics

• Enzyme kinetics studies the rates of enzyme-catalyzed reactions and how these rates change with experimental parameter adjustments.
• Turnover Number: Equivalent to the number of substrate molecules transformed into products by a single enzyme molecule under maximum substrate conditions.

Factors Affecting Enzyme Activity

• Temperature: Most enzymes show optimal activity between 30-40°C and are significantly inactivated at around 45°C.
• pH: Enzyme stability is often broader than the pH range of optimal activity.
• Water Activity (Aw): Enzyme activity directly correlates with water activity. Activity increases as Aw values approach 1.0 (saturation).

Enzyme Inhibitors

• Reversible Inhibitors: Competing substrate, binding to active sites.
• Irreversible Inhibitors: Forming covalent bonds with critical functional groups of the enzyme.

Regulatory Enzymes

• These enzymes control the rate of metabolic pathways.
• They might change catalytic activity through allosteric mechanisms or covalent modifications.

Immobilized Enzymes

• Enzymes are physically or chemically confined within a limited space.
• This confinement provides advantages like repeated use, high biocatalytic activity using small enzyme amounts, continuous catalytic processes, and cost-effectiveness

Questions for Reflection

• Questions about various aspects of enzymes and their applications.

This quiz explores the roles and regulations surrounding the Nomenclature Committee of the International Union of Biochemistry and Molecular Biology. It includes questions that test your understanding of key phrases and the purpose of the content provided, as well as the significance of document handling instructions. Test your knowledge on nomenclature's impact in biochemistry.