Enzymology: Catalysis Flashcards
Enzyme Def.
Proteins that function as biological catalysts, altering the rate of the reaction without being changed itself
Why enzymes are important
Chemical reactions require them to proceed at effective rate for body function. Direct all metabolic events in body (thus any enzyme failure results in reduced body function)
Black Urine Disease Outline
Defect in enzyme homogenistate 1,2- deoxygenase necessary for processing cdertain amino acids. Homogenestic acid builds up in body damaging tissues and coloring urine black
Enzyme Diagnostic Tool Functions
Enzyme presence/absence in patient samples can be used as indicators of disease. Eg Liver tests for aminotransferase diagnosing hepatocellular injury, biliary obstruction or hypothyroididm
Enzymes Shape and Composition
Globular with active site shape complementary to 1 specific substrate. Some contain a co-factor (non-protein component). Localise to 1 spot
Types of Enzymes
Oxidoreductase, Transferase, Hydrolases, Lyases, Isomerases and Ligases
Oxidoreductase Function
Adds/ removes H+ from molecules
Transferase Functions
Transfers C-, N- or P-
Hydrolases Function
Cleaves bonds and adds -OH
Lysases Function
Cleaves C-C, C-S and C-N bonds
Isomerase Function
Changes isometric shape
Ligases Function
Forms new bonds
Active Site Outline
Specific chape to only bind a few substrates. Protects substrate from external environment and holds it in place
How enzyme and substrate combine
electroststic attraction (opposite charges) and complementary shape
How enzyme converts substrate into product
Substrate pushed into ‘transition state’ (high energy) and bonds change within substrate
How do enzymes speed up the rate of the reaction
They lower the activation energy
Enzyme Initial Rate
Slowest. Low substrate conc
Enzyme Optimum Rate
Medium Rate. Enzymes at their most effuicent. Substrate to product ratio is pretty much equal
Enzyme Maximum Rate
Fastest rate possible. Significantly higher substrate then product concentration
Enzyme Rate (V) Def.
Number of substrate molecules converted to product per unit time. Unit: micro-mole per minute
Michaelis-Menton Plot Outline
x-axis: Substrate conc. y-axis: velocity. Begins almost linear but begins to plateu when reaching Vmax. Established under conditions of fixed temp and pH
Vmax Def.
The fastest an enzyme can convert substrate to product.
Km (Michealis Constant) Def.
The substrate concentration when we reach 50% Vmax. This indicates the affinity an enzyme has for it’s substrate. Lower Km (less solute conc required for 50% Vmax) = higher affinity
Practical Applications of Km
Defines optimal solute concentration to use in lab to measure enzyme reactions
Substrate Concentration Notation
[S]
Michaelis-Menton Plot to Lineweaver-Burk Plot Conversion
A curved line to straight. Line now crosses both x and y axises enabling more accurate readings of Vmax and Km. Equation of line is inverted to reciprocal
Lineweaver-Burk Line plot
x-axis: 1/[S], y-axis: 1/V0
Lineweaver-Burk Plot y =mx + c
1/V0 = (Km/Vmax)(1/[S]) + 1/Vmax
5 Factors Regulating Enzymes
Temp, pH, substrate conc., cofactor/coenzyme and enzyme inhibition
Temperature outline
Enzymes operate best at 35-40 degrees C. Velocity increases proportionally with temp until point of denaturation is reached (irreversable)
pH Outline
Optimum varies with different enzymes. Denaturation can occur
What types of enzymes have a sigmoid (slow start, accelarion, plateus at end) curve and why
Allosteric. HAs multiple sub units + active sites leading it to not obey Michaelis Kinetics
Cofactor Def.
Inorganic metal ions attached to enzymes
Coenzymes Def.
Organic molecules (eg vitamins)
Apoenzyme Def.
Enzyme without cofactor. Inactive
Holoenzyme Def.
Enzyme with cofactor. Active
Prosthetic Enzyme Def.
Coenzyme tightly bound to enzyme
Inhibitor Def.
Substance that diminishes the velocity of an enzyme-catalyzed reaction. 2 Types
Irreversible Inhibitor Def.
Form covalent bonds. Can’t reagin activity
Reversible Inhibitor Def.
Non-covalent bonds. Dilution of enzyme-inhibitor complex recovers activity. 2 Types
Competitive Reversable Inhibitors
Bind to active sites. Preventing enzyme bonding
Non-competitive Reversable Inhibitors
Doesn’t bind to active sites but prevents enzyme converting substrate into product
