ENZYMES Flashcards
(98 cards)
1
Q
Define a prosthetic group
A
Is a nonprotein components that are bound covalently or very tightly to proteins
2
Q
what is coenzyme
A
Is a less tightly bound nonprotein components
3
Q
wha is a cofactor
A
Metal ions and simple organic compounds that participate in enzyme catalysis
4
Q
Define apoenzyme
A
a complex of prosthetic groups or cofactors with nonfunctional proteins
5
Q
What is a holo enzyme
A
Is a complex of prosthetic groups or cofactors with functional groups
6
Q
Define enzymes
A
Are biological proteins with catalytic properties
7
Q
How do enzymes influence chemical transformations?
A
Enzymes determine the pattern of chemical transformations by facilitating reactions between substrates.
8
Q
Are all enzymes proteins? Provide an exception and explain.
A
Yes, most enzymes are proteins, but there’s an exception: ribozymes, which are RNA molecules with catalytic functions.
9
Q
Describe the structure of conjugated enzymes and explain the roles of prosthetic groups or coenzymes
A
Conjugated enzymes consist of two parts:
1. Apoenzyme: The protein component.
2. Prosthetic group or coenzyme: The non-protein part that enhances enzyme activity.
10
Q
What is clinical enzymology, and how is it applied in disease diagnosis and treatment?
A
Clinical enzymology applies enzyme science to diagnose and treat diseases. It involves measuring specific enzyme levels in blood or tissues to identify health conditions.
11
Q
what is the role of activators
A
Activators increase the rate of enzyme catalyzed reaction
12
Q
What are co-enzymes and activators, and how do they impact enzyme-catalyzed reactions
A
Co-enzymes are organic molecules that assist enzymes in their catalytic functions. Activators are substances that enhance the rate of enzyme-catalyzed reactions. They achieve this by binding to the enzyme or its substrate, leading to increased reaction efficiency.
13
Q
How do metal ions contribute to the structure and function of certain enzymes?
A
Some enzymes incorporate metal ions as an essential part of their structure. These ions play critical roles in maintaining enzyme stability, facilitating substrate binding, and promoting catalysis.
14
Q
What happens when metal ions are removed from enzymes using EDTA
A
The removal of integral metal ions (using EDTA) causes a conformational change in the enzyme. This alteration disrupts the active site, rendering the enzyme inactive.
15
Q
How can an enzyme be reactivated after metal ion removal?
A
Enzyme reactivation can occur through two methods
1. Dialysis: The enzyme is dialyzed against a solution containing the appropriate metal ion, allowing it to rebind and regain activity.
2. Metal Ion Addition: Adding the specific metal ion back into the reaction mixture can also reactivate the enzyme
16
Q
what are some of the common activators
A
- magnesium
- manganese
- zinc
- potassium
- calcium
17
Q
What are the roles of metal ions in enzymes
A
- They help in either maintaining or producing (or both), active structural conformation of the enzyme
- Formation of enzyme-substrate complex
- Making structural changes in substrate molecule
- Accept or donate electrons
- Formation of ternary complexes with enzyme or substrate.
18
Q
Which activators are reuired by enzymes as anions as activators
A
Some enzymes require chloride and bromide anions as activators.
19
Q
Do some enzymes need more than one metal activator
A
Yes, some enzymes indeed require multiple metal activators.
20
Q
How do coenzymes compare to activators in terms of complexity?
A
Coenzymes are more complex molecules than activators
21
Q
What are NAD and NADP, and how do they differ structurally?
A
NAD and NADP are coenzymes. NADP is structurally similar to NAD but has an additional phosphate group attached
22
Q
Which cellular processes involve NAD
A
NAD participates in glycolysis and most of the citric acid cycle reactions during cellular respiration
23
Q
What are coenzymes, and how do they differ from substrates?
A
Coenzymes are small organic molecules that assist enzymes in catalyzing reactions. Unlike substrates, which are directly involved in the reaction, coenzymes do not undergo any chemical changes during the process.
24
Q
Name two common coenzymes.
A
- NAD (Nicotinamide Adenine Dinucleotide)
- NADP (Nicotinamide Adenine Dinucleotide Phosphate)
24
What role do NAD and NADP play during the reaction?
NAD and NADP bind to the enzyme during the reaction. Some coenzymes bind loosely, while others tightly associate with the enzyme’s active center, facilitating the catalytic process.
24
How do NAD and NADP affect the rate of enzymatic reactions?
The rate of enzymatic reactions influenced by NAD and NADP follows the Michaelis-Menten pattern. As substrate concentration increases, the rate of the reaction initially rises but eventually levels off due to enzyme saturation.
24
where does coenzymes and prosthetic groups derived from
vitamins
25
What happens to NAD and NADP during a reaction involving an enzyme?
NAD and NADP slightly bind to the enzyme during the reaction, with some tightly binding and forming part of the active center.
26
What is a coenzyme referred to when it is bound to an enzyme?
is referred to as a prosthetic group.
27
Give an example of a prosthetic group and mention the enzymes it is associated with
Pyridoxal-5-phosphate (p-5-p) is a prosthetic group for ALT (alanine transaminase) and AST (aspartate transaminase) enzymes.
28
How are many coenzymes and prosthetic groups derived?
Many coenzymes and prosthetic groups are derived from vitamins
29
Mention the 6 classes of enzymes
1. Oxidoreductases
2. Transferases
3. Hydrolases
4. Lyases
5. Isomerases
6. Ligases
30
What is oxidoreductases
Oxidoreductases are enzymes that catalyze oxidation-reduction reactions. These reactions involve the transfer of electrons between molecules.
31
Provide examples of oxidoreductases
1. Alcohol dehydrogenase: Catalyzes the oxidation of alcohols to aldehydes or ketones.
2. Lactate dehydrogenase: Involved in the conversion of lactate to pyruvate.
3. Xanthine oxidase: Converts xanthine to uric acid.
4. Glutathione reductase: Participates in the reduction of glutathione disulfide (GSSG) to its reduced form (GSH).
5. Glucose-6-phosphate dehydrogenase: Plays a role in the pentose phosphate pathway1.
32
What do transferases do, and what type of group transfer reactions do they catalyze?
Transferases catalyze the transfer of a functional group (other than hydrogen) from one substrate to another. They facilitate group transfer reactions.
33
mention the examples of transferases
1. Aspartate transaminase (AST) and alanine transaminase (ALT): Involved in amino acid metabolism.
2. Hexokinase: Transfers a phosphate group to glucose during glycolysis.
3. Phosphoglucomutase: Catalyzes the conversion of glucose-1-phosphate to glucose-6-phosphate.
4. Hexose-1-phosphate uridyltransferase: Participates in galactose metabolism.
5. Ornithine carbamoyl transferase: Plays a role in the urea cycle1.
34
What are hydrolases, and what type of reactions do they catalyze?
Hydrolases are enzymes that catalyze hydrolysis reactions, breaking down molecules by adding water.
35
What do lyases do, and how do they differ from hydrolases?
Lyases catalyze the removal of groups from substrates without hydrolysis, resulting in a product that contains a double bond. Unlike hydrolases, lyases do not use water during the reaction
36
What is the role of isomerases, and what types of isomers do they interconvert?
Isomerases facilitate the interconversion of geometric, optical, or positional isomers.
37
Describe the function of ligases, and what energy-rich compound is involved?
Ligases catalyze the joining of two substrate molecules, coupled with breaking of the pyrophosphate bond in adenosine triphosphate (ATP) or a similar compound.
38
what are examples of hydrolases
1. glucose-6-phosphatate. Catalyzes the hydrolysis of glucose 6-phosphate, resulting in the creation of a phosphate group
2. pepsin. digests proteins, particularly those in meat, eggs, seeds, or dairy products
3. trypsin. Trypsin is an enzyme that helps digest proteins in the small intestine
4. Esterases. Esterases are a class of enzymes that catalyze the hydrolysis of esters into an acid and an alcohol.
5. Glycoside hydrolases. Glycoside hydrolases break down glycosidic bonds in complex sugars, such as cellulose, hemicellulose, and starch.
39
what are the examples of lyases
1. Fumarase. also known as fumarate hydratase, catalyzes the hydration of fumarate to malate
2. Arginosuccinase. participates in the urea cycle
3. Histidine Decarboxylase. responsible for the decarboxylation of histidine
40
What do isomerases catalyze, and what types of isomers do they interconvert?
Isomerases catalyze the interconversion of geometric, optical, or positional isomers. These enzymes facilitate the rearrangement of atoms within a molecule
41
what are the examples of isomerases
retinal isomerase (involved in vision) and triosephosphate isomerase (in glycolysis).
42
what are the examples of ligases
1. Aminoacyl-tRNA synthetase (aaRS) plays a crucial role in protein synthesis.
2. Glutamine synthetase catalyzes the formation of glutamine from glutamate and ammonia
3. DNA ligases are enzymes that join DNA fragments
43
What are isoenzymes
A group of related enzymes catalyzing the same reaction but having different molecular structure and physical and immunological properties
44
Where can isoenzymes be found within the body?
Isoenzymes may occur within a single organ or within a single cell.
45
How has the presence of multiple forms of enzymes in human tissue benefited medical research?
It has facilitated the study of human disease.
46
What does the presence of isoenzymes allow in terms of antibody production?
The presence of isoenzymes allows the production of specific antibodies to specific molecular structures.
47
What role does enzyme-specific antisera play in immunoassay?
1. Target Capture: The ELISA plate is coated with a capture antibody specific to the target antigen being investigated.
2. Antigen-Antibody Interaction: The sample containing the target antigen is introduced to the plate, allowing it to bind to the capture antibody.
3. Enzyme-Linked Antibody Introduction: Enzyme-linked antibodies, which are enzyme-conjugated versions of antibodies specific to the target antigen, are then added. Thes antibodies bind to the target antigen captured in the previous step.
48
How do isoenzymes contribute to our understanding or treatment of diseases?
By allowing for the production of specific antibodies, facilitating targeted studies, and enabling precise immunoassays.
49
What is first-order kinetics in enzyme reactions?
First-order kinetics refers to a reaction whose rate is dependent on the substrate concentration.
50
Define zero-order kinetics.
Zero-order kinetics occurs when the reaction rate only depends on enzyme concentration.
51
How does substrate concentration affect a first-order kinetic reaction?
In first-order kinetics, the rate of reaction is directly proportional to the substrate concentration.
52
What happens to the rate of a zero-order kinetic reaction as substrate concentration increases?
The rate remains constant because it only depends on enzyme concentration.
53
What are the implications of first-order kinetics in enzyme-catalyzed reactions?
First-order kinetics allow us to understand how substrate concentration influences reaction rates and enzyme activity.
54
How can zero-order kinetics impact enzyme inhibition studies?
Zero-order kinetics can help identify enzyme inhibitors that directly affect enzyme concentration without substrate involvement
55
What are the three types of enzyme specificity?
1. Stereochemical specificity
2.Reaction specificity
3. Substrate specificity.
56
What is Stereochemical specificity in enzymes?
It refers to the fact that only one of the isomers (D or L-isomers) acts as a substrate for an enzyme action.
57
Explain reaction specificity in enzymes
Reaction specificity means that one enzyme can catalyze only one reaction in a series of reactions.
58
What does substrate specificity refer to in enzymes?
Substrate specificity can be absolute (acting on one specific substrate) or relative (closely related substrates).
59
What is the significance of bond specificity in enzymatic reactions
Bond specificity indicates that proteolytic enzymes act specifically on particular bonds within substrates.
60
Give an example of stereochemical specificity in enzyme-substrate interactions
An example is how only one isomer (e.g., D-glucose) is recognized by hexokinase during glycolysis.
61
How does reaction specificity impact metabolic pathways
Reaction-specific enzymes ensure that each step in a metabolic pathway is precisely controlled.
62
What role does substrate specificity play in drug design?
Substrate specificity guides the development of drugs that selectively target specific enzymes.
63
Can an enzyme exhibit both absolute and relative substrate specificity
Yes, some enzymes can show both absolute specificity for a single substrate and relative specificity for closely related substrates.
64
How do proteolytic enzymes recognize specific bonds for cleavage?
Proteolytic enzymes have specific active sites that recognize and cleave particular peptide bonds.
65
What is the rate of enzymatic reaction directly proportion to
directly proportional to the amount of active enzyme present in the system
66
What is the relationship between the rate of an enzyme reaction and the amount of active enzyme present in the system?
The rate of an enzyme reaction is directly proportional to the amount of active enzyme present. As enzyme concentration increases, the reaction rate also increases.
67
How is the rate of an enzyme reaction determined under controlled conditions?
The rate of an enzyme reaction is determined by measuring the change in substrate concentration or the formation of product over time. Controlled conditions ensure consistent parameters such as temperature, pH, and substrate concentration
68
What methods can be used to determine enzyme reaction rate (enzyme activity)?
Both fixed time (measuring the reaction at a specific time point) and continuous monitoring (measuring the reaction continuously) methods can be used to determine enzyme activity.
69
How is the progress of an enzyme reaction rate monitored?
The progress of an enzyme reaction rate is monitored by observing the change in absorbance due to either a decrease in substrate concentration or an increase in product concentration. This change in absorbance provides insight into the reaction kinetics.
70
Mention 5 factors that influence enzyme reactions
1. substrate concentrations
2. enzyme concentration
3. PH
4. temperature
5. inhibitors
6. cofactors
71
How do immunoassay methodologies quantify enzyme concentration by mass?
Immunoassay methods use specific antibodies to detect and quantify enzymes based on their mass. These techniques are commonly used for enzyme quantification
72
What is the significance of establishing a linear relationship between enzyme quantity and enzyme activity?
The linear relationship ensures that enzyme activity can be accurately inferred from the measured enzyme quantity. However, this relationship must be determined individually for each enzyme.
73
How are electrophoretic techniques used to quantify enzymes
Electrophoresis separates enzymes based on their charge and size. By comparing their migration patterns to known standards, enzyme quantities can be estimated.
74
What are the advantages and limitations of using immunoassay methodologies for quantifying enzymes
Advantages: High specificity, sensitivity, and ability to measure low enzyme concentrations. Limitations: Requires specific antibodies, potential interference, and cost considerations.
75
How do isoforms and isoenzymes contribute to our understanding of enzyme function and diversity?
Isoforms and isoenzymes are variants of the same enzyme with distinct properties. Studying them helps reveal tissue-specific functions, evolutionary adaptations, and disease markers.
76
How are enzymes used as reagents to measure non-enzymatic serum constituents?
Enzymes are employed to quantify non-enzymatic serum constituents such as glucose, cholesterol, and uric acid. Their specificity ensures accurate measurement of these analytes.
77
What is the advantage of using immobilized enzymes for batch analyses?
Immobilized enzymes offer greater convenience for batch analyses. They remain stable and can be reused, making them more practical than enzymes in solution.
78
Name three non-enzymatic serum constituents that can be measured using enzymes as reagents.
Glucose, cholesterol, and uric acid.
79
How does the specificity of enzymes contribute to accurate measurements?
Enzymes specifically recognize their target analytes, ensuring precise quantification without interference from other substances.
80
What solid support media can be used to immobilize enzymes?
Enzymes can be immobilized on solid supports like cellulose and agarose.
81
How are enzymes used in medicine to detect tissue injury?
Enzymes are measured in serum and other body fluids to detect injury as they are released from the damaged tissue.
82
What is the significance of measuring enzymes within a tissue?
It helps identify abnormalities or absence of the enzyme, which may lead to disease.
83
How do injuries to tissues provide information about damage?
Injuries release cellular substances including enzymes that serve as plasma markers of tissue damage.
84
What is the role of tissue-specific isoenzymes or isoforms in diagnostic enzymology?
They can be evaluated to enhance tissue and organ specificity, helping identify the exact location of damage or disease.
85
How does changes in the serum activities of enzymes aid medical diagnosis?
These changes help understand the location and nature of pathologic changes in tissues of the body.
86
Why is it necessary to understand factors affecting enzyme release and their clearance rate?
It’s crucial for interpreting changes that occur in disease conditions, aiding accurate diagnosis and treatment planning.
87
What information can be obtained by analyzing enzymes found predominantly in specialized tissues?
This analysis can provide specific insights into potential injuries or diseases associated with those particular specialized tissues.
88
How do cellular substances including enzymes act as plasma markers?
They indicate tissue damage when released into plasma following an injury.
89
mention 4 sources of enzymes in serum
1. leakage from cells
2. efflux of enzymes from damaged cells
3. altered enzyme production
4. clearance enzymes
90
What causes leakage of enzymes from cells?
Leakage occurs due to irreversible cell injury, which reduces the integrity of the cell membrane, allowing macromolecules including enzymes to escape from intracellular components.
91
How is the rate of enzyme escape from damaged cells controlled
Once leakage of enzymes from cells is established, the rate of escape is presumably controlled by diffusion gradient.
92
What factors can lead to altered enzyme production
Altered enzyme production may result from a genetic deficiency or when enzyme production is depressed due to disease.
93
How are most enzymes removed from the body?
Most enzymes are removed by the reticuloendothelial system, and some are excreted by the kidney, controlling their half-life in plasma.
94
What consequence can reduced enzyme clearance have?
Reduced clearance of enzymes may lead to an increased concentration of enzymes in plasma
95
what does the selection of enzyme test depend on
1. distribution of enzymes among various tissues
2. knowledge of the intracellular location of enzymes
3. the clearance way and the rate at which its activity disappears from the blood
