Enzymes Flashcards
What is a ribozyme?
An RNA molecule that can catalyze a biochemical reaction
What is an Abzyme?
A product produced in the lab by attaching an antibody to the active site structure isolated from an enzyme
What’re the two models for enzyme structure and function?
- Lock/Key
- Induced Fit
What nonprotein components are essential for enzyme activity?
- Prosthetic groups: Nonroteiin organic structures tightly bound to enzyme ex. Heme in cytochrome C
- Coenzymes: Less tightly bound substance frequently derived from vitamins
- Cofactors: Metal ions or simple organic molecules
What are the classifications of enzymes?
- Oxidoreductase
- Tranferase
- Hyrdolase
- Lyase
- Isomerase
- Ligase
What type of reaction is catalyzed by an Oxidoreductase?
Redox rxns (Addition/removal of e-)
What type of reaction is catalyzed by a Tranferase?
Transfer of a specific group (phosphorylation, etc)
What type of reaction is catalyzed by a Hydrolase?
Bond breakage via H20
What type of reaction is catalyzed by a Lyase?
Bond breakage w/h out water
What type of reaction is catalyzed by an Isomerase?
Formation of an Isomer (ex group switching trans/cis)
What type of reaction is catalyzed by a Ligase?
Bond formation (ex carboxylation)
How does pH affect pH?
- Enzymes operate optimally about some particular pH. Activity drops off in a bell shaped curve around that pH
- Due to chaired groups at active sites or salt bridges =becoming titrated
Ho does temperature affect enzyme activity?
- there is an optimal temperature for enzyme activity
- Temperature increases kinetic activity until a certain point at which the protein starts to denature
What are isozymes?
Enzymes from the same species which have the same activity, but differ in chemical structure and kinetic properties
Heat is the Michealis-menton equation?
V = Vmax[S] / [S] + Km
What is the reaction velocity at very low [S]?
V = Vmax[S] / Km
What is the reaction velocity at very high [S]?
V = Vmax
How does enzyme concentration affect Km?
It doesn’t
How is enzyme Km related to binding affinity?
Smaller Km, Higher affinity
How are reaction rates related to dissociation contants?
- When K2<
What is the line weaver-Burk equation?
What is the slope?
What is it’s usefulness in medicine?
1/V = Km/Vmax x 1/[S] x 1/Vmax
Slope = Vmax
Used to identify inhibitors
What is the equation for the Eddie-Hofstra plot?
V = {-Km(V)} / [S]
What are the two types of inhibitors, and how do they affect Km and Vmax?
Irreversible: Removes some enzyme from reaction mixture; only affects Vmax
Reversible: Can affect either or both Km or Vmax
What is an example of beneficial irreversible inhibition?
Penicillin for inhibiting glycopeptuide transpeptidase in staph. Aureus
What are the three types of reversible inhibitors?
- Competitive
- Uncompetitive
- Noncompetitive
What is an example of competitive inhibition?
Rate-limiting step for Cholesterol biosynthesis
Reduction of 3 hydroxymethylglutaryl Coa to Mevalonate and CoAsh
What is an example of noncompetitive inhibitors?
Lead poisoning causing anemia
What is an example of uncompetitive inhibitors?
Lithium inhibition of Inositol phosphatase
Manic depression
How are allosteric enzyme regulated?
- Either inhibited or activated by effectors binding to a site other than the active site
What are the states of an allosteric enzyme?
R State - More Active (relaxed)
T State - Less active (Taut)
What is an example of allosteric regulation?
Regulation of aspartame transcarboxylase to produce N-Carbamoyl Aspartate
How is K calculated for Allosteric enzymes?
K = [S]^n x [Vmax - V] / V
When is a lineweaver Burke plot linear for an allosteric enzyme?
When n = 1
