3 - Enzymes – general concept of enzyme catalysis. Chemical nature of the enzyme molecules Cofactors (coenzymes and prosthetic groups) – chemical nature. Active site. Enzyme specificity. Enzyme classification and nomenclature.

sections

• what is enzyme catalysis

• enzymes as biological catalysts

• chemical nature of enzyme molecules

• cofactors, coenzymes and prosthetic groups

• cofactor examples

• enzyme names and their classification

• active site of an enzyme

• what is enzyme catalysis

• increase in rate of process due to biological molecule “an enzyme”

• enzymes as biological catalysts

• Enzymes are responsible for most chemical reactions and homeostasis in the body

• Localised in tissues and body fluids

• Intracellular enzymes catalyse internal metabolic processes

• Plasma membrane enzymes respond to signals and help transport substances across membranes

• Enzymes are biological catalysts:

  • Speed up reactions but do not alter equilibrium

  • Do not increase the amount of product formed

  • Remain unchanged after the reaction

• chemical nature of enzyme molecules

• Enzymes are proteins (macromolecule component)

• Simple enzymes: made only of proteins

• Complex enzymes (holoenzymes):

  • Apoenzyme = protein part

  • Cofactor = non-protein part

• Prosthetic group: small organic molecule covalently bound to apoenzyme

• Coenzyme: small organic molecule non-covalently bound to apoenzyme

• cofactors, coenzymes and prosthetic groups

• Cofactor: Non-protein chemical or metal ion needed for enzyme activity

• Types of cofactors:

  • Prosthetic group: Small organic molecule covalently bound to apoenzyme

  • Coenzyme: Small organic molecule non-covalently bound

• All cofactors (prosthetic groups + coenzymes) are essential for enzyme function

• cofactor examples

• nucleotide derivatives - ATP, UDP, CDP

• porphyrins - heme

• quinones - ubiquinone

• thiol compounds - glutathione, lipoic acid

• enzyme names and their classification

• Olly Thought Holly Liked Issacs Lolly

• Olly Thought Holly Liked Issacs Lolly

• oxidoreductase - add or remove H atoms or electrons

• Transferase - transfer of functional groups

• Hydrolase - adding water to a bond

• Lyases - adding water, ammonia or CO2 across double bonds or remove these

• Isomerases - changing L-conformation to D-conformation

• Ligases - 2 chemical groups joined with use of ATP

Enzyme specificity - enzymes act in a specific way towards a reaction so have specific substrates, spring, group, bond, steric isomer and geometric isomer specificity

• active site of an enzyme

• Substrates bind to the enzyme's active site, which is complementary in shape

• Binding occurs via weak bonds (sometimes covalent)

• Active site is a 3D cleft or pocket formed during tertiary/quaternary folding

• In complex enzymes, cofactors are part of the active site

• Amino acid residues in the active site play roles in catalysis and binding