Classification, Nomenclature and Kinetics

Question 1

In enzyme commission numerical code, the nomenclature always starts with E.C. followed by the four digits.

Explain the representation of each digit: (1-4)

Answer 1

• First digit- represents enzyme’s class
• Second digit- represent enzyme’s subclass
• Third digit- represent enzyme’s sub subclass
• Fourth digit- represent enzyme’s serial number specific to the enzyme sub subclass

Question 2

Enumerate the classification of enzymes in order: (6)

Answer 2

1. Oxidoreductase
2. Transferase
3. Hydrolase
4. Lyase
5. Isomerase
6. Ligase

Question 3

these enzymes catalyze redox reaction between substrates; these enzymes utilize
coenzymes

Answer 3

Oxidoreductase

Question 4

Enzymatic reaction of Oxidoreductase

Answer 4

A- + B → A + B-

Question 5

enzymes that catalyze the transfer of specific chemical group other than hydrogen ions
between substrates

Answer 5

Transferase

Question 6

specific type of transferase that would catalyze the transfer of phosphate group from one substrate to another

Answer 6

Kinase

Question 7

Enzymatic reaction of Transferase

Answer 7

A-X(chemical grp) + B → A + B-X

Question 8

these are enzymes that catalyze the hydrolysis of various chemical bonds

Answer 8

Hydrolase

Question 9

Requirement in order for Hydrolase to function

Answer 9

there must be water in able to function

Question 10

Enzymatic reaction of Hydrolase

Answer 10

A–B + H2O → A–OH + B–H

Question 11

enzymes that catalyze the removal of chemical groups from substrates without hydrolysis

Answer 11

Lyase

Question 12

In lyase, the product retains what type of bond?

Answer 12

Double bond

Question 13

Enzymatic reaction of Lyase

Answer 13

ATP → cAMP + PPi

Question 14

Enzymes that catalyze the interconversion of the geometric optical and positional isomers;
would catalyze the interconversion of substrate A to become substrate B

Answer 14

Isomerase

Question 15

Enzymatic reaction of Isomerase

Answer 15

A → B

Question 16

enzymes that catalyze the joining of two substrate molecules coupled with the breaking of
pyrophosphate bond in ATP

Answer 16

Ligases

Question 17

Enzymatic Reaction of Ligase

Answer 17

Ab + C → A–C + b

Question 18

Enzymes catalyze physiologic reactions by increasing the activation energy level that the reactants must reach. The greater the required activation energy the longer the reaction to proceed.

a. First statement is true, second statement is true.
b. First statement is false, second statement is true.
c. First statement is true, second statement is false.
d. First statement is false, second statement is false.

Answer 18

b. First statement is false, second statement is true.

Enzymes catalyze physiologic reactions by DECREASING/LOWERING the activation energy level that the reactants must reach

Question 19

The lower the activation energy required the slower the formation of the product

a. True
b. False

Answer 19

b. False

Lower activation energy = faster formation of product

Question 20

In catalytic mechanism of enzymes, relationship between enzymes, substrate, and product occurs.

Enumerate the relationship/specificity of enzymes: (4)

Answer 20

1. Absolute specificity
2. Group specificity
3. Bond specificity
4. Stereoisomeric specificity

Question 21

Relationship between enzymes, substrate, and product:

Explain absolute specificity

Answer 21

Enzymes combined with only one substrate and catalyze only one corresponding reaction

Question 22

Relationship between enzymes, substrate, and product:

Explain group specificity

Answer 22

enzymes combined with all substrates containing a particular group

Question 23

Relationship between enzymes, substrate, and product:

Explain bond specificity

Answer 23

enzyme reaction is specific to chemical bonds

Question 24

Factors that Influence Enzymatic Reactions: (7)

Answer 24

1. Substrate Concentration
2. Enzyme Concentration
3. pH
4. Temperature
5. Cofactors
6. Storage
7. Hemolyzed samples

Question 24

Relationship between enzymes, substrate, and product: Explain stereoisomeric specificity

Answer 24

enzymes that combined with only one optical isomer

Question 25

Reaction rate is proportional to the substrate concentration with the activity a. Zero-order kinetics b. First order kinetics

Answer 25

b. First order kinetics

Question 26

Only a fixed number of substrate (in excess) is converted to product per second a. Zero-order kinetics b. First order kinetics

Answer 26

a. Zero-order kinetics

Question 27

Enzyme Level: _______ = Normal Enzyme Level: ________ - Clinically significant a. Low - Low b. Low - High c. High - Low d. High - High

Answer 27

b. Low - High

Question 28

Most of the physiologic reaction occur in which pH range

Answer 28

pH = 7.0 to 8.0

Question 29

If the enzyme pH is too basic or too acid it could inactivate/denature enzyme. There is no exemption in this rule. a. First statement is true, second statement is true. b. First statement is false, second statement is true. c. First statement is true, second statement is false. d. First statement is false, second statement is false.

Answer 29

c. First statement is true, second statement is false. Phosphatases are exempted in this rule.

Question 30

These enzymes could react in extremely high or low pH

Answer 30

Phosphatase

Question 31

assay temperature should be constant within what degree

Answer 31

± 0.1°C

Question 32

Optimum temperature for enzymatic activity

Answer 32

37°C

Question 33

Temperature range where protein denaturation starts and start of decreasing enzyme activity

Answer 33

40°C to 50°C

Question 34

Temperature range where proteins are inactivated

Answer 34

60°C to 65°C

Question 35

Temperature Coefficient(Q10) for every 10°C increase in temperature, there will be two-fold increase in enzyme activity. For storage, it should be at refrigerator temperature at 20°C or colder for maintaining enzymatic activity. a. First statement is true, second statement is true. b. First statement is false, second statement is true. c. First statement is true, second statement is false. d. First statement is false, second statement is false.

Answer 35

c. First statement is true, second statement is false. For storage, it should be at freezer temperature at (-)20°C or colder. *emphasis on the negative sign

Question 36

Why is multiple freezing and thawing of serum is not allowed?

Answer 36

It could damage or destroy the enzymes in the serum which results to false decrease of enzymes.

Question 37

What is the refrigerator temperature ideal for the storage of substrate and coenzyme?

Answer 37

2°C to 8°C

Question 38

What is the ideal storage temperature of serum sample wherein the target is LDH?

Answer 38

Room temperature

Question 39

What can falsely increase enzyme concentration?

Answer 39

Hemolyzed samples

Question 40

What could falsely decrease the enzyme concentration?

Answer 40

Milky specimens/ Lipemic samples

Question 41

Measurement of catalytic activity: (3)

Answer 41

1. Dependent on enzyme concentration 2. Always performed in zero-order kinetics 3. Performed during the linear phase of reaction

Question 42

General methods of measuring enzymatic reaction: (2)

Answer 42

1. Fixed-time (Two point) Assay 2. Continuous monitoring

Question 43

General methods of measuring enzymatic reaction: The reagents are combined, the reaction proceeds, the reaction is stopped and the amount of reaction is measured.

Answer 43

Fixed-time (Two point) Assay

Question 44

General methods of measuring enzymatic reaction: Multiple measurements at specific time intervals or continuous measurement as absorbance changes. 30-60s interval; absorbance is noted.

Answer 44

Continuous monitoring

Question 45

An expression of the relationship between the velocity of the enzyme reaction and the substrate concentration

Answer 45

Michaelis-Menten Equation

Question 46

Calculation of Enzyme Activity: The amount of enzyme that will catalyze the reaction of 1 μmol of substrate per minute.

Answer 46

IU (EC)

Question 47

Calculation of Enzyme Activity: The amount of enzyme that will catalyze the reaction of 1 mol of substrate per second

Answer 47

Kat (SI)

Question 48

Enzyme Theories: The shape of the key(substrate) must fit into the lock(enzyme)

Answer 48

Emil Fisher's/ Lock and Key theory

Question 49

Enzyme Theories: Based on the substrate binding to the active site of the enzyme

Answer 49

Kochland's Induced Fit theory