(F) L1: Enzymes (Part 1) Flashcards by Kchianna Lauren Coronel

Enzymes hasten chemical reactions in (organic/inorganic) matter as they are biologic catalysts

Organic

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TOF: Enzymes are capable of catalyzing multiple chemical reactions which serve as the basis for their classification

False (single/limited amount)

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Enzymes are large molecules found (inside/outside) the cell

Inside

Note: They are involved in the processes within the cell

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Increased membrane permeability allows enzymes to (enter/exit) the blood

Enter

Note: This allows for their measurement in the lab

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TOF: Enzymes are measured directly (their absolute value in the blood sample)

False (measured in terms of activity)

Note: You don’t measure how much enzyme is present in the sample

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Enzymes appear in serum after cellular (growth/injury)

Injury

Note: They also appear after cellular degeneration or from storage areas

It’s because they are found INSIDE the cell

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If enzymes are found in the serum, it most likely correlates to what?
A. Organ damage
B. Organ regeneration
C. Organ transplant

A. Organ damage

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Enzymes are specific for their what in order to convert it into a defined product?

Substrates

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Enzymes tend to react with a number of substrates which can lead to what reaction?

Cross-reactivity

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What do you call the reaction wherein an enzyme only reacts with one substrate?

Absolute Reaction

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This is a water-free cavity where the substrate interacts/binds with

Active Site

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This is a cavity other than the prior site which binds regulator molecules

Allosteric Site

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In order to catalyze certain reactions, enzymes are required to first bind to a substrate which produces what complex?

Enzyme-Substrate (ES) Complex

Note: Only then will the enzyme release/produce a product

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This refers to when enzymes stay intact after the synthesis of products

Reusability of the enzyme

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Factors Affecting Enzymatic Reactions

In enzyme concentrations, the higher the concentration, the (faster/slower) the reaction

Faster

Note: A higher # of enzymes can accomodate more substrates

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Factors Affecting Enzymatic Reactions

This principle states that when the substrate concentration reaches its maximal value, higher concentration substrates no longer result in increased rate of reaction

Saturation Kinetics

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Factors Affecting Enzymatic Reactions

S1: The rate of reaction will decrease when additional substrates are added
S2: When all enzymes are occupied, the additional substrates will remain functional and the rate of reaction will remain steady

Which among the statements is true?

Both are false

S1: Will increase
S2: Substrates will be deemed useless

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Cofactors

These are your second substrates
A higher value of this signifies an increased reaction velocity
Is in combination with a cofactor and apoenzyme
Is essential for absolute enzymatic activity

e.g. NAD and NADP

Coenzyme

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Cofactors

Which among the 2 is the inactivated enzyme and the active enzyme?

A. Holoenzyme
B. Apoenzyme

Inactivated = Apoenzyme
Activated = Holoenzyme

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Cofactors

What is formed when:
Cofactor + Apoenzyme + Coenzyme

Holoenzyme

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Cofactors

The more coenzyme present, the (higher/lower) the velocity of the reaction

Higher (meaning “faster”)

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Cofactors

Nicotinamide adenine dinucleotide (NAD) and Nicotinamide adenine dinucleotide phosphate (NADP) are considered?

A. Apoenzymes
B. Holoenzymes
C. Coenzymes

C. Coenzymes

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Cofactors

These are inorganic ions (Ca, Zn, Cl, Mg, and K)
They alter the spatial configuration of the enzyme for proper binding
Are mostly electrolytes

Activators

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Cofactors

These are inorganic ions attached to a molecule
Can act as enzymes themselves even though they aren’t called as such
e.g. Catalase and Cytochrome Oxidase

Metalloenzymes

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These inhibit enzymatic reactions

Inhibitors

# Types of Inhibitors - This assembles in the form of a substrate compatible with a specific enzyme allowing it to bind to the active site - It competes for the same site against the original substrate - The reaction is reversible - Can result to an excess in substrates - Can decrease the velocity of the reaction (Km)

Competitive Inhibitor

# Types of Inhibitors Refers to the the property of being able to be removed from the active site which gives the substrate a chance to retrieve its original site

Reversibility

# Types of Inhibitors Why do inhibitors result in an excess in substrate? A. More substrates are released in the presence of inhibitors B. Binding sites are occupied by the inhibitors C. Binding sites select the inhibitors more than the substrates

B. Binding sites are occupied by the inhibitors

# Types of Inhibitors A graphical representation of saturation kinetics

Michaelis-Menten Curve

# Types of Inhibitors - Refers to the substrate concentration at which the reaction velocity is half of the maximum level - It is constant for a specific enzyme and substrate under a defined reaction condition - An expression of the relationship between the velocity of an enzymatic reaction and substrate concentration

Michaelis-Menten Constant

# Types of Inhibitors - Refers to the the relationship between the rate of reaction and the substrate - States that the rate of reaction will initially increase as more substrate is added but will later remain constant when the maximum level is reached

Saturation Kinetics

# Types of Inhibitors TOF: In the presence of competitive inhibitors, the velocity (Km) changes

True

# Types of Inhibitors - This does not compete with the substrate since it targets the allosteric site - It alters the shape of the active site which prevents binding of the substrate thereby decreasing the reaction - The action is irreversible

Non-competitive Inhibitors

# Types of Inhibitors - This binds to an ES complex rather than the enzyme - An increase in substrate leads to an increase in ES complexes thereby increasing inhibition

Uncompetitive Inhibitors

# Types of Inhibitors What type of inhibitor is this referring to? Competes for the same site

Competitive

# Types of Inhibitors What type of inhibitor is this referring to? Targets the allosteric site

Non-competitive

# Types of Inhibitors What type of inhibitor is this referring to? Binds to an ES complex

Uncompetitive

# Types of Inhibitors What type of inhibitor is this referring to? The reaction is reversible

Competitive

# Types of Inhibitors What type of inhibitor is this referring to? The reaction is irreversibe

Non-competitive

# Types of Inhibitors What type of inhibitor is this referring to? It alters the shape of the active site

Non-competitive

# Factors Affecting Enzymatic Reactions - These are variations of one enzyme which provides minute changes in the characteristics of each - It provides the same catalytic reaction but has a slightly different molecular structure which varies in amino acid sequences

Isoenzymes

# Factors Affecting Enzymatic Reactions TOF: Isoenzymes make it easier to isolate the activity of the target enzyme

False (more difficult) ## Footnote Note: A single substrate may react with ALL of the isoenzymes making it non-specific

# Factors Affecting Enzymatic Reactions TOF: Isoenzymes increase enzymatic activity

True

# Factors Affecting Enzymatic Reactions S1: Isoenzymes have an indirectly proportional relationship with enzymatic activity S2: Isoenzymes have a directly proportional relationship with the easiness of isolating the activity of the target enzyme Which of these statements is false?

Both are false (reverse the relationships)

# Factors Affecting Enzymatic Reactions What is the optimum temperature for enzymatic activity?

37ºC | Note: 25º, 30º, and 37º is the range of values

# Factors Affecting Enzymatic Reactions At what temperatures are enzymes denatured resulting in a decreased rate of reaction?

40-50ºC

# Factors Affecting Enzymatic Reactions At what temperatures are enzymes inactivated?

60-65ºC

# Factors Affecting Enzymatic Reactions An increase in temperature increases the movement of what resulting in an increased rate of reaction?

Molecules

# Factors Affecting Enzymatic Reactions What is this principle: For every 10ºC increase, there is a two-fold increase (2x) in enzymatic activity

Temperature Coefficient (Q10)

# Factors Affecting Enzymatic Reactions What is the optimum pH for enzymatic physiologic reactions?

Between 7-8

# Factors Affecting Enzymatic Reactions An extreme pH level may result to the ff. EXCEPT: A. Denaturation B. Alteration of the covalent state of the enzyme C. Structural changes D. Changes in the charge of amino acid residues

B. (should be ionic state)

# Factors Affecting Enzymatic Reactions These are used to stabilize the pH for enzymatic reactions

Buffers

# Factors Affecting Enzymatic Reactions Complete the statements to make them true: 1. Storing enzymes at low temperatures will make them (reversibly/irreversibly) inactive 2. Refrigeration/freezing is an (ideal/undesirable) way of storing enzymes with the exception of LDH 3. Repeated thawing and freezing will result to (denaturation/inhibition)

1. Reversibly 2. Ideal 3. Denaturation

# Factors Affecting Enzymatic Reactions LDH is stored ideally at RT especially its coenzymes LD4 and LD5 as they are (heat-labile/cold-labile)

Cold-labile | Note: May lead to falsely decreased values

# Factors Affecting Enzymatic Reactions Fill in the missing numerical values: 1. A prolonged preservation will require a temperature of atleast (blank) 2. Temperatures of (blank) to (blank) are the ideal storage temperatures for substrates and coenzymes

1. -20ºC 2. 2ºC to 8ºC

# Factors Affecting Enzymatic Reactions When there is hemolysis, enzymes are released into the circulation and will result to a falsely (increased/decreased) enzyme concentration

Increased

# Factors Affecting Enzymatic Reactions This factor refers to the example of the presence of TAGs which decreases enzyme concentration

Lactescence or Milky specimen

# Enzyme Nomenclature 1. 1st Digit 2. 2nd/3rd Digit 3. 4th Digit A. Serial number B. Classification C. Subclass

1. B 2. C 3. A

# Enzyme Nomenclature This was standardized by what organization?

Enzyme Commission (EC)

# Enzyme Nomenclature Enzymes are classified according to the ff. EXCEPT: A. Biochemical function B. Substrate catalyzed C. Class of reaction catalyzed D. Activation energy

D. Activation energy

# Enzyme Classification Function: The removal or addition of electrons (redox) Examples: Cytochrome oxidase (CO), Lactate dehydrogenase (LDH), Malate dehydrogenase (MDH), Isocitrate dehydrogenase (ICD), and G6PD

Oxidoreductase

# Enzyme Classification Function: The transfer of a chemical group other than hydrogen from one substrate to another Examples: Creatine kinase (CK), Aspartate aminotransferase (AST), Alanine aminotransferase (ALT), and Ornithine transcarbamylase (OTC)

Transferase

# Enzyme Classification Function: The hydrolysis or splitting of a bond by the addition of water Examples: Esterase, Acid phosphatase (ACP), Alkaline phosphatase (ALP), Chalcone synthase (CHS), and Lipase (LPS)

Hydrolase

# Enzyme Classification Function: The removal of groups from substrates without hydrolysis with products containing double bonds Examples: Glutamate decarboxylase, Pyruvate decarboxylase, Tryptophan decarboxylase, and Aldolase (ALD)

Lyase

# Enzyme Classification Function: Catalyze the intramolecular arrangement of the substrate compound Examples: Glucose phosphate isomerase and Ribose phosphate isomerase

Isomerase

# Enzyme Classification Function: The joining of two substrate molecules coupled with the breaking of pyrophosphate bonds in ATP or similar compounds Examples: Synthase

Ligase

# Enzyme Theories - Presented by Emil Fisher - The shape of the substrate must fit into the enzyme

Lock and Key Model

# Enzyme Theories - Presented by Kochland - The substrate binds to the active site of the enzyme (gives emphasis on the presence of the active site)

Induced Fit Theory

# Enzyme Kinetics Greater amount of free energy in the substrate + lesser amount of free energy on the product = ? | Note: Free energy = kinetic energy

Increased chemical reaction

Refers to the ability of an enzyme to react to a specific substrate

Enzyme Specificity

# Enzyme Specificity - It combines with only one substrate and catalyzes only one reaction - The most preferred as it directly measures the target enzyme/substrate

Absolute Specificity

# Enzyme Specificity This combines with all the substrates in a chemical group

Group Specificity

# Enzyme Specificity This reacts with specific chemical bonds

Bond Specificity

# Enzyme Reactions - This depends on enzyme concentration - Methods of determining these are expensive hence the preference for the other kind of reaction

Zero-order

# Enzyme Reactions - Is directly proportional to substrate concentration - e.g. a decrease in the number of substrate indicates a decrease in the number of enzymes

First-order

# General Methods of Assay - Enzymes will be measured once on a designated time - Reactants will first be combined, then a reaction will take place on a designated time - The reaction will be stopped and measured

Fixed Time (Endpoint Method)

# General Methods of Assay Multiple measurements are done and is more preferred over fixed time

Continuous Monitoring (Kinetic Assay)

# Units for Enzymatic Activity - The conventional unit - 1 micromole of substrate per minute (umol/min)

International Unit (IU or U)

# Units for Enzymatic Activity - 1 mole of substrate per second (mol/sec) - 1 IU = 16.7 or 17 of this unit - 1 of this unit = 0.06 IU/L

Katal Unit (KU)

TOF: Since most laboratories utilize the enzyme itself in measuring enzyme levels, the units for enzymatic activity focuses more on its concentration

False (amount of substrate) ## Footnote Remember: Enzymes are quantified based on their activity rather than absolute values

Enzymes are quantified based on their activity which depends on the ff. EXCEPT: A. A change in substrate concentration B. A change in product concentration C. A change in apoenzyme concentration

C. (must be coenzyme)

Units used to report enzyme levels are called as?

Activity Units | Must consider a change in pH, temperature, substrate, etc.

# Causes of Elevated Plasma Levels Impaired removal of enzymes from (serum/plasma) which may be related to renal function e.g. Amylase is freely-filtered in the kidneys therefore damage in the kidneys may cause problems regarding its removal

Plasma

# Causes of Elevated Plasma Levels (Increased/Decreased) cell membrane permeability

Increased

# Causes of Elevated Plasma Levels Increase in the production of (cells/stimulating hormones) such as malignancies and the like

Cells (↑ cells = ↑ enzymes)

# Causes of Elevated Plasma Levels (Increased/Decreased) cell turnover/apoptosis

Increased | Note: Early destruction may lead to increased enzymes in the circulation

# Causes of Elevated Plasma Levels Decreased (clearance/release) of enzymes from the circulation may be related to renal function

Clearance

# Causes of Elevated Plasma Levels (Cell/Tissue) necrosis and degeneration due to external factors

Tissue

Familiarize with the 10 factors affecting enzymatic reactions

1. Enzyme concentration 2. Substrate concentration 3. Cofactors 4. Inhibitors 5. Isoenzymes 6. Temperature 7. Hydrogen ion concentration (pH) 8. Storage 9. Hemolysis 10. Lactescence/milky specimen

Familiarize with the 6 causes of elevated plasma enzyme levels

1. Impaired removal of enzyme from plasma 2. Increased permeability of cell membrane 3. An increase in the number of cells or the production of cells such as malignancies and the like 4. An increase in the normal cell turnover or apoptosis 5. Decreased clearance of enzymes from the circulation 6. Tissue necrosis and degeneration

(F) L1: Enzymes (Part 1) Flashcards

(90 cards)