Enzyme pt. 2 (Quiz 1) Flashcards
Enzymes are classified according to the ___?
type of reaction they catalyze
Classification of Enzymes
- EC First Integer: ____ of enzyme catalyzed reactions
- 2nd integer: a ___
- 3rd number: ___ depending on 1st and 2nd integer
- 4th number: ____
Classification of Enzymes
* six major classes
* a subclass
* subclassification
* serial number
_______
rate of a reaction between ____ molecules is ____ if they are abstracted from ____ and held in ____ proximity to each other (in the enzyme’s active site)
Facilitation of Proximity
* two
* enhanced
* dilute solution
* close
to increase the effective concentration of the reactants
Propinquity effect
In Covalent catalysis – amino acid side chains :
nucleophilic groups
This mechanism involves the transient covalent binding of the substrate to an amino acid residue in the active site. Generally, this is to the hydroxyl group of a serine, although the side chains of threonine, cysteine, histidine, arginine and lysine can also be involved.
covalent catalysis
Modes of Enhancement of Rates of Bond Cleavage / Catalytic Mechanisms (8)
- Facilitation of Proximity
- Covalent Catalysis
- General Acid-Base Catalysis
- Binding Energy
- Metal-ion Catalysis
- Strain
- Molecular Distortion, and Shape Change
- Strain and Distortion Model
- The binding of the substrate results in the distortion of the substrate in a way that makes the chemical reaction easier
this would determine the ionization state of an amino acid side chain
pH of the active site
For acid-base catalysis, _____ is the most versatile amino acid due to its pk, which means that in most physiological situations it can act as either a proton donor or proton acceptor.
histidine
refers to weak acids
proton donors
refers to weak bases
proton acceptors
______
- The preceding ____ groups can potentially serve as either proton donors or proton acceptors.
- This is ____ on many factors including the ____ nature of the substrate, any ____ involved, and the ___ of the active site
- Generally,these ____ will interact together with the ____, or in conjunction with water or other weak, organic acids and bases found in cells.
- acid-base catalysis
- functional
- dependent, molecular, co-factors, pH
- amino acids, substrate
_____
- is involved in a majority of ____ reactions . it needs to be distinguished from ____ acid-base catalysis.
- the _____ aids in stabilizing the transition state via ____ of a proton.
- Therefore, the rate of the _____ is dependent on the _____ as well as the appropriate ____ state.
General Acid-Base Catalysis
* enzymatic
* specific
* buffer
* donation or removal
* reaction
* buffer concentration
* protonation
catalytic factors in the binding of a substrate and enzyme:
1) transient____ of substrate and enzyme ____ by reducing the ______ of the two molecules,
2) solvation ____ of the _____ thermodynamically favorable, and
3) substrate and enzyme _____ changes.
- limiting
- movement
- relative motion (or entropy)
- distruption
- water shell
- conformational
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
_______
- Various metals, all ____ charged and including zinc, iron, magnesium, manganese and copper, are known to form ____ with different enzymes or substrates.
- This ____ complex can aid in the _____ of the substrate in the ______, and
- metals are known to mediate _____ reactions by ____ changes in their ____ states (like Fe³+ to Fe2+).
Metal lon Catalysis
- positively
- complexes
- metal-substrate-enzyme
- orientation
- active site
- oxidation-reduction
- reversible
- oxidation
Clinical Use of an Enzyme pt.2
- Enzyme activity can be ____ genetically
- A _____ in an enzyme can alter its ____ affinity, co-factor ____ stability etc. which can be used as a _____ in comparison with ____ enzyme
- Loss of _____ presence due to genetic mutation as detected by ____ enzyme substrate and/or lack of ____ leading to a _____
- NOTE: _____ that identify specific messenger RNA or DNA sequences are replacing many ____ enzymatic based markers of genetic disease
- altered genetically
- mutation
- substrate
- binding
- diagnostic
- normal
- enzyme
- increased
- product
- dysfunction
- PCR techniques
- traditional
Clinical Use of Enzyme pt. 1
- Enzyme Activity in Body Fluids Reflects ____ Status
- Enzyme Activity Reflects the Presence of ____ or _____
- Activity of serum enzymes _____ in presence of an _____
(ex. some insecticides inhibit serum cholinesterases) - Determine co-factor ____(like an essential vitamin) by ____
(ex. add back vitamin to assay, if activity increases, suggests deficiency in that vitamin)
- Organ
- Inhibitors or Activators
- decreases
- inhibitor
- deficiencies
- enzyme activity
An ____ is a blood test or urine test that measures levels of certain enzymes to assess how well the body’s systems are functioning and whether there has been any tissue damage.
enzyme test
Common Enzymes used for clinical diagnosis
- alanine aminotransferase (ALT, also called glutamate pyruvate transaminase, GPT)
- alkaline phosphatase
- amylase
- aspartate aminotransferase
- creatine kinase
- lactate dehydrogenase
– evaluate liver function and diagnose liver diseases such as hepatitis and cirrhosis.
alanine aminotransferase
assess liver and bone disorders. when levels are elevated it can indicate cholestasis (bile flow obstruction), liver disease, or bone diseases such as Paget’s disease
alkaline phosphatase
diagnose acute pancreatitis, and other conditions like salivary gland infections or intestinal obstruction
amylase
assess liver function. Elevated levels can indicate liver damage but can also be associated with heart or muscle injury
aspartate aminotransferase
diagnose muscle damage, including conditions like myocardial infarction (heart attack) and rhabdomyolysis
creatine kinase
diagnosis of various conditions, including hemolysis, liver disease, and certain cancers (tissue damage)
lactate dehydrogenase
Chemical reaction need an initial input of energy
THE ACTIVATION ENERGY
During this part (activation energy) the reaction of the molecules are said to be in a ?
Transition state
Enzyme makes the reactions go faster by…
- Increasing the ____ make molecules move faster
- _____ systems are very sensitive to _____ changes.
- Enzymes can increase the _____ of reaction without increasing/requiring an increase in the ______
- They do this by lowering the _ energy.
- They create a new reaction pathway “a ____”
- temperature
- Biological, temperature
- rate of reactions, temperature.
- activation energy.
- “a short cut”
Enzyme Specificity
- Enzymes have varying degrees of ____for substrates
- Enzymes may recognize and catalyze:
o a ___ substrate
o a ___ substrate
o a particular type of bond
- specificity
o single
o group of similar
Lock-and-Key Model
In the lock-and-key model of enzyme action:
- The active site has a ___ shape.
- Only substrates with the ____ shape can fit.
- The ____ is a key that fits the lock of the ___ .
- rigid shape.
- matching shape
- substrate,
- active site
The Lock and Key Hypothesis
- Temporary structure called the _____ complex formed
- Products have a different ____ from the substrate
- Once formed, they are ____ from the ____
- Leaving it ___ to become attached to another ____
- This explains enzyme specificity
- This explains the loss of activity when enzymes denature
- enzyme-substrate
- shape
- released, active site
- free, substrate
Enzyme changes shape with substrate
people-pleaser na enzyme
Induced Fit Theory
The induced-fit model of enzyme action:
- The active site is ____, not rigid.
- The shapes of the enzyme, active site, and substrate ____ the fit, which improves _____.
- There is a ___ range of ____ specificity..
- flexible,
- adjust to maximum,
- catalysis.
- greater range,
- substrate specificity
The Induced Fit Hypothesis
- Some proteins can ___ their shape (______)
- When a substrate combines with an ____, it induces a change in the enzyme’s ____
- The active site is then ____ into a ____ conformation making the __ environment suitable for the reaction
- The ____ of the substrate are ___ to make the reaction ___ (lowers activation energy)
- change, (conformation)
- enzyme,
- conformation
- moulded, precise, chemical
- bonds, stretched, easier
Enzyme Catalyzed Reactions
- When a substrate (S) fits properly in an active site, an ____ complex is formed:
E + S ⇌ ES -
Within the active site of the ES complex, the reaction. occurs to ___ substrate to product (P):
ES → E + P - The **products are then ___ **, allowing another substrate molecule to ___ the enzyme
o this cycle can be repeated millions (or even more) times per minute
- The overall reaction for the conversion of substrate to product can be written as follows:
E + S ⇌ ES → E + P
- enzyme-substrate (ES)
- convert:
- released
- bind
Enzymatic reaction steps
1) Substrate approaches active site
2) Enzyme-substrate complex forms
3) Substrate transformed into products
4) Products released
5) Enzyme recycled
Enzyme Kinetics
Enzyme activity can be assayed in many ways
o disappearance of substrate
o appearance of product
o continuous assay
o end point assay
The ___ of an enzyme-catalyzed reaction is dependent upon the ____
velocity (V), substrate concentration [S]
at _, . A significant amount of substrate has not yet been converted to product.
initial velocity of a reaction
at this point, addition of more substrate will not increase the rate of the reaction
maximal velocity of a reaction
The ___ describes the kinetic behavior of many enzymes
Michaelis-Menten equation
Michaelis-Menten equation
o maximum rate that can be observed in the reaction
o substrate is present in excess
o enzyme can be saturated (zero order reaction)
at Vmax
o a constant that is related to the affinity of the enzyme
for the substrate
o units are in terms of concentration
michaelis constant, Km
Enzymes are never expressed in terms of their ____ (as mg or µg etc.) but are expressed only as ____.
concentration, activities.
- ____ moles of substrate converted to product per unit time.
o The rate of appearance of ___ or the rate of disappearance of ____
o Test the absorbance: __
- Enzyme activity
o product, substrate
o spectrophotometer
Factors affecting enzyme activity
- Concentration of substrate
- Concentration of enzyme
- Temperature
- PH
- Activators
- Inhibitors
the increased in velocity is proportional to the substrate concentration
Substrate concentration: non-enzymatic reaction
, a faster reaction occurs but it reaches a saturation point when all the enzyme molecules are occupied.
substrate concentration: enzymatic reactions
Elevated alkaline phosphatase levels can indicate ____ (bile flow obstruction), liver disease, or bone diseases such as _____ disease
- cholestasis
- Paget’s disease
