Enzyme Flashcards
proteins that are catalysts of biochemical reactions.
Enzymes
not consumed during a
chemical reaction.
Catalyst
Typically has a
globular shape. It has a complex 3-D structure.
Enzymes
First clear recognition of enzyme was made by ?
Payen and Persoz (around 1833)
an alcohol precipitate of malt extract contained in a thermolabile substance that converted starch to sugar.
Diastase
use of -ase in naming enzyme
Duclaux (1898)
first to crystallize enzyme (urease)
J.B. Sumner (1924-1930)
modulates an enzyme activity
Effectors
found in animal and plant cells
Catalase
found in saliva and in the pancreas. It breaks down starch down to
maltose.
Amylase
synthesize enzyme (builds up). It builds/combines multiple
Glucose-1-Phosphate molecules into starch
Potato Phosphorylase
characteristic of catalyst. High efficiency, 10^3 to 10^17 faster
than the corresponding uncatalyzed reactions.
Catalytic efficiency
a characteristic of catalyst. High _________, interacting with one
or a few specific substances and catalyzing only one type of chemical reaction.
Specificity
characteristic of catalyst, 37β, physiological pH, ambient atmospheric pressure.
Mild reactions conditions
a part of the enzyme where the reactants bind, where the biochemical reaction occurs.
Active Site
The enzyme active site is usually composed of?
amino acid side chains interact,
metal ions, various types of polar, non-polar, ionic interactions.
a region within an enzyme that fits the shape of molecules called substrates or reactants.
Active Site
The active site containsβ¦
amino acid R groups that align and bind the substrate.
The substrates fit like a key in a lock and the active site is the lock itself. If the conditions are satisfied, a chemical reaction will occur to form products. After the reaction, the enzyme is unchanged.
βLock and Key Modelβ
additional non-protein molecule that is needed by some enzymes to help the reaction
Cofactors
Cofactors that are bound and released easily are called
Coenzymes
present in trace amounts within the enzyme.
Metal Ions
a cofactor for carboxypeptidase
Zn^2+
non-protein or organic, maybe a vitamin
Coenzyme
catalyze the same reaction in different tissues in the body
Isoenzymes
which converts lactate to pyruvate consists of five isoenzymes.
Lactate dehydrogenase
first created the classifications in enzyme system
IUPAC (International Union for Pure and Applied Chemistry)
developed the four-integer number system and a name.
EC or the Enzyme Commission
Enzymes are classified according to the type of reaction they catalyze:
a. Oxidoreductases
oxidation-reduction reactions.
Enzymes are classified according to the type of reaction they catalyze:
b. Transferases
transport/transfer of group of atoms or single atoms
Enzymes are classified according to the type of reaction they catalyze:
c. Hydrolases
Hydrolysis
Enzymes are classified according to the type of reaction they catalyze:
d. Lyases
adding or removing atoms to form a double bond.
Enzymes are classified according to the type of reaction they catalyze:
e. Isomerases
rearranging atoms
Enzymes are classified according to the type of reaction they catalyze:
f. Ligases
using ATP to combine molecules (substrates).
EC first integer:
six major classes of enzyme catalyzed reactions.
Second integer:
a subclass
Third integer:
sub classification depending on 1st and 2nd integer.
Fourth integer:
serial number
rate of reaction between two molecules is enhanced if
they are abstracted from dilute solution and held in close proximity to each other
Facilitation of Proximity
This mechanism involves the transient covalent bonding of the substrate to an amino acid residue in the active site.
Covalent Catalysis
more prone to undergoing covalent catalysis reactions
nucleophilic groups
many reactions involve the formation of normally unstable, charge intermediates.
General Acid-Base Catalysis
accounts for the overall lowering of activation
energy for a reaction, and it can also be considered as a catalytic mechanism for a reaction.
Binding Energy
β various metals, all positively charged including zinc, iron,
magnesium, manganese, and copper are known to form complexes with different
enzymes or substrates.
Metal Ion Catalysis
The binding of the substrate
results in the distortion of the substrate in a way that makes the chemical reaction easier
Strain, Molecular Distortion, and Shape Change
Common enzymes used for clinical diagnosis
alanine aminotransferase
(ALT, also called glutamate pyruvate transaminase GPT), alkaline phosphatase,
amylase,
aspartate aminotransferase, creatine kinase, and
lactate dehydrogenase.
the reaction is in between the reactant consumption and
product formation (peak).
Transition State
Increasing the temperature make molecules
move faster
very sensitive to temperature changes
Biological systems
Enzymes can increase the rate of reactions without?
increasing/requiring an increase
in the temperature.
they catalyze one type of reaction for a single substrate.
Absolute Enzymes
they catalyze one type of reaction for similar substrates
group enzymes
they catalyze one type of reaction for a specific type of bond.
linkage enzymes
The lock and key hypothesis
- Temporary structure called the enzyme-substrate complex formed.
- Products have a different shape from the substrate.
- Once formed, they are released from the active site.
- Leaving it free to become attached to another substrate.
Induced fit theory
- Enzyme changes shape with substrate.
- The active site is not rigid.
- The active site is capable of changing its shape depending upon the substrate.
the active site is flexible, not rigid, the shapes of the enzyme, active site, and substrate adjust to maximum the fit which
improves the catalysis, and there is a greater range of substrate specificity
induced fit model of enzyme action
The induced fit hypothesis:
- Some proteins can change their shape (conformation).
- When a substrate combines with an enzyme, it induces a change in the enzymeβs
conformation. - The active site is then molded into a precise conformation.
- Making the chemical environment suitable for the reaction.
- The bonds of the substrate are stretched to make the reaction easier (lowers
activation energy).
When a substrate (S) fits properly in an active site, what is formed?
an enzyme-substrate complex
(ES)
πΈ + π β πΈπ (πππ£πππ ππππ)
Within the active site of the ES complex, what happened?
the reaction occurs to convert substrate to product (P):
πΈπ β πΈ + π (πππππ£πππ ππππ)
The overall reaction for the conversion of substrate
πΈ + π β πΈπ(πππ£πππ ππππ) β πΈ + π (πππππ£πππ ππππ)
Enzymatic reaction steps
- Substrate approaches the active site
- Enzyme-substrate complex forms
- Substrate transformed into products
- Products released
- Enzyme recycled (depends on the enzyme, not always)
The reaction for the sucrase catalyzed hydrolysis of sucrose to glucose and fructose.
ππ’ππππ π + ππ’ππππ π β πΈπ πππππππ₯ (πππ£πππ ππππ) β ππ’ππππ π + πΊππ’πππ π + πΉππ’ππ‘ππ π (πππππ£πππ ππππ)
