bio

• biological catalysts


  Enzymes are usually proteins that act as
• lowering the activation energy


  An enzyme speeds a reaction by ________, changing the reaction pathway that provides a lower energy route for conversion of substrate to product
• globular proteins, simple proteins, conjugated proteins


  Most enzymes are_____; some are _____, others are ______
• simple enzyme


  composed only of protein (amino acid chains)
• conjugated enzymes


  Has a non-protein part in addition to a protein part
• apoenzyme


  protein part; inactive in itself
• cofactor


  inorganic moiety; the activator; loosely bound to protein
• coenzyme


  nonprotein inorganic
• holoenzyme


  apoenzyme + cofactor (biologically active conjugated enzyme)
• •type of reaction catalyzed

  •identity of the substrate


  Most commonly named with reference to their function:
• subatrate


  A _____ is the reactant in an enzyme-catalyzed reaction
• 1. Suffix -ase identifies it as enzyme

  
  

  2. Type of reaction catalyzed by an enzyme is often used as a prefix

  
  

  3. Identity of substrate is often used in addition to the type of reaction


  Three important aspects of the naming process
• 1. Oxidoreductases

  2. Transferases

  3. Hydrolases

  4. Lyases

  5. Isomerase

  6. Ligases


  Six major classes of enzymes based on the types of reaction they catalyzed:
• Oxidoreductase


  catalyzes an oxidation-reduction reaction
• Transferase


  catalyzes the transfer of a functional group from one molecule to another
• Kinases & Transaminases


  Two major subtypes of transferase?
• Hydrolase


  catalyzes a hydrolysis reaction
• Carbohydrases


  hydrolyze glycosidic bonds in oligo and polysaccharides
• Proteases


  effect the breaking of peptide linkages in proteins
• Lipases


  effect the breaking of ester linkages in triacylglycerols
• Lyase


  catalyzes the addition or the removal of a group in a manner that does not involve hydrolysis or oxidation
• Dehydratase


  effects the removal of the components of water to form double bond
• Hydratase


  effects the addition of the components of water to a double bond
• Decarboxylase


  effects the removal of carbon dioxide from a substrate
• Deaminase


  effects the removal of ammonia from a substrate
• Ligase


  catalyzes the formation of a bond between two molecules involving ATP hydrolysis to ADP
• Synthetases


  formation of new bond between two substrates with participation of ATP
• Carboxylases


  formation of new bond between substrate and carbon dioxide with participation of ATP
• Active site


  it is where the substrate binds to enzyme
• Intermediate reaction species


  Formed when the substrate binds with the active site.
• Two models for substrate binding to enzyme

  •Lock-and-Key model

  •Induced Fit model
• Long-and-Key- model


  in this model, the active site has a fixed, rigid geometrical confirmation
• Induced Fit model


  the active site has a flexible shape that can change to accept a variety of related substrates
• •H-bonding

  •Hydrophobic interactions

  •Electrostatic interactions


  Forces that determine substrate binding
• Absolute, Stereochemical, Group and Linkage specificity

  4 enzyme specificity
• Absolute specificity


  catalyze a particular reaction for only one substrate
• Stereochemical specificity


  distinguish between stereoisomers
• L-amino acid oxidase


  catalyzes reactions of L-amino acids but not of D-amino acids
• Group specificity


  involves structurally similar compounds that have the same functional groups
• Linkage specificity


  involves a particular type of bond irrespective of the structural features in the vicinity of the bond