ENZYMES PART 1 Flashcards
Dehydrogenase
Removes hydrogen
Two way function, can catalyze backward reaction
Major Classes of Enzymes
EC 1: Oxidoreductase
EC 2: Transferase
EC 3: Hydrolases
EC 4: Lyases
EC 5: Isomerases
EC 6: Ligases
EC 7: Translocases
Reaction rate
Higher
Reaction condition
Mild
Reaction specificity
Specific
Activity regulation
Regulated under normal condition
Systematic Name
Substrate:Cosubstrate Major Class
EC1: Oxidoreductase
Redox reaction
Elimination reaction
EC2: Transferases
Transfer of groups
Substitution reaction
EC3: Hydrolase
Hydrolysis
Uses H2O to break covalent bonds
EC4: Lyases
Covalent bond breaking
Produces double bond (e.g. o==o)
EC5: Isomerases
Isomers
Exchange of functional groups
EC6: Ligases
Formation of new covalent bond
ATP as an activtor of the substrate
Convert poor leaving group into a good leaving group
Synthase
No ATP
Synthetase
Uses ATP
EC7: Translocases
Extracellular to intracellular
Uses ATP for conformation changes
Isozymes
Enzymes with quaternary structure
Combination of subunits differs in different tissues
Useful in diagnosing sites of tissue, injury, cell death
Enzymes that have same substrate, classification, reaction but with different amino acid residues and specificity and regulation
Isozymes
Isomer enzymes
Isozymes
Structures of enzyme
Active site
Binding site
Catalytic site
Substrate
Cosubstrate
Binding site
Where substrate and cosubstrates bind
Catalytic site
Near the binding site
Where catalysis happens
Important binding interactions
H bond
Ionic bond
Hydrophobic interactions
Transition state
Bonds are in the process of being formed and broken
Structure resembles that of the unstable intermediate
Not likely to be as characterized as those of its reaction occuring
More theoretical, unstable
Cannot be isolated
Transition state
Unstable intermediate
A chemical species with just formed bonds
Exists at lower energy possibly between the energy peaks of 2 transition states
Could be isolated or chemically trapped (usuallt at lower temp)
Unstable intermediate
Substrate binding
Lock and key
Induced fit model
Specificity of activity
Reaction specificity
Absolute specificity
Group specificity
Linkage specificity
Optical specificity
Geometric specificity
Reaction specificity
For specific reaction
Ex. Oxidoreductase for redox reaction not for phosphorilization
Absolute specificity
For specific substrate
Ex. Glucokinase for glucose but not for other hexose
Group specificity
Target specific functional group
Ex. Hexokinase for any hexose
Linkage specificity
For specific linkage
Ex. Amidase hydrolyze amide linkages but not ester
Optical (stereo) specificity
For specific D/L configuration
Ex. L-aminoacyl esterase catalyzes the reaction of L-amino acyl but not D-amino acyl
Geometric specificity
For specific shape/geometry
Ex. Aromatic acyl aminoesterase for aromatic compounds
Cofactors
Metal ions
Prosthetics
Coenzymes
Metalloenzymes
Tightly bound
Transition metals: Fe2+ Fe3+ Cu2+ Zn2+
Metal enzymes
Losely bound
Alkali and akaline earth metals: K Na Ca Mg
Prosthetics Group
Non amino acid residues
Covanlently bound to the enzyme
Dialyzable
Thermostatble
Coenzymes
Non protein organic molecules
Transiently associated
Redox and transfer reactions
Precursor: vitamins
Holoenzyme
Fully functional form of the enzyme
Apoenzyme and cofactor
Apoenzyme
Protein only w/o cofactor
Inactive
Nonfunctional
