Enzymes

Question 1

specific biologic proteins that catalyze biochemical reactions
without altering the equilibrium point of the reaction or being consumed or
changed in composition.

Answer 1

Enzymes

Question 2

The different forms may be differentiated from each other based on
certain physical properties, such as electrophoretic mobility, solubility, or
resistance to inactivation.

Answer 2

isoenzyme

Question 3

results when an enzyme is subject to posttranslational modifications.

Answer 3

isoform

Question 4

a nonprotein molecule, called a

_____, may be necessary for enzyme activity.

Answer 4

cofactor

Question 5

Inorganic cofactors, such as

chloride or magnesium ions, are called

Answer 5

activators.

Question 6

is an organic

cofactor, such as nicotinamide adenine dinucleotide (NAD).

Answer 6

coenzyme

Question 7

When bound tightly

to the enzyme, the coenzyme is called a

Answer 7

prosthetic group.

Question 8

The enzyme portion ______, with its respective coenzyme, forms a complete and active
system, a ______.

Answer 8

apoenzyme; holoenzyme

Question 9

Catalyze an oxidation–reduction reaction between two

substrates

Answer 9

Oxidoreductases.

Question 10

Catalyze the transfer of a group other than hydrogen from

one substrate to another

Answer 10

Transferases.

Question 11

Catalyze hydrolysis of various bonds

Answer 11

Hydrolases.

Question 12

Catalyze removal of groups from substrates without hydrolysis; the
product contains double bonds

Answer 12

Lyases.

Question 13

Catalyze the interconversion of geometric, optical, or

positional isomers

Answer 13

Isomerases.

Question 14

Catalyze the joining of two substrate molecules, coupled with
breaking of the pyrophosphate bond in adenosine triphosphate (ATP) or a
similar compound

Answer 14

Ligases.

Question 15

The excess energy, called
_________, is the energy required to raise all molecules in 1 mole of a
compound at a certain temperature to the transition state at the peak of the
energy barrier.

Answer 15

activation energy

Question 16

refers to enzymes that predominantly combine

with only one optical isomer of a certain compound.

Answer 16

Stereoisomeric specificity

Question 17

the reaction rate is

directly proportional to substrate concentration.

Answer 17

first-order kinetics

Question 18

the reaction rate depends only on enzyme

concentration.

Answer 18

zero-order kinetics

Question 19

is the substrate concentration at which

the reaction velocity is half of the maximum level.

Answer 19

Michaelis-Menten constant (Km)

Question 20

more accurate and convenient
determination of Vmax and Km may be made through a ____________, a
double-reciprocal plot of the Michaelis-Menten constant,

Answer 20

Lineweaver-Burk plot

Question 21

For each __ degree increase in temperature, the rate

of the reaction will approximately double

Answer 21

10

Question 22

The rate of denaturation increases as the temperature

increases and is usually significant at

Answer 22

40°C to 50°C.

Question 23

physically bind to

the active site of an enzyme and compete with the substrate for the active site.

Answer 23

Competitive inhibitors

Question 24

binds an enzyme at a place other than the active
site and may be reversible in the respect that some naturally present metabolic
substances combine reversibly with certain enzymes.

Answer 24

noncompetitive inhibitor

Question 25

the inhibitor binds to the ES complex—increasing substrate concentration results in more ES complexes to which the inhibitor binds and, thereby, increases the inhibition.

Answer 25

Uncompetitive inhibition

Question 26

has the ability to bind to either the E or ES complex at a different site from the substrate active site.

Answer 26

mixed | inhibitor

Question 27

Vmax | unaltered; Km appears increased.

Answer 27

Competitive inhibition

Question 28

Vmax decreased; | Km unchanged.

Answer 28

Noncompetitive inhibition

Question 29

Vmax decreased; Km appears | decreased.

Answer 29

Uncompetitive inhibition

Question 30

a convenient method of | enzyme quantitation is measurement of

Answer 30

catalytic activity.

Question 31

One of two general methods may be used to measure the extent of an enzymatic reaction:

Answer 31

fixed-time and continuous-monitoring or kinetic assay

Question 32

the reactants are combined, the reaction proceeds for a designated time, the reaction is stopped (usually by inactivating the enzyme with a weak acid), and a measurement is made of the amount of reaction that has occurred.

Answer 32

fixed-time method,

Question 33

multiple measurements, usually of absorbance change, are made during the reaction, either at specific time intervals (usually every 30 or 60 seconds) or continuously by a continuous- recording spectrophotometer.

Answer 33

continuous-monitoring or kinetic assays,

Question 34

the amount of enzyme that will catalyze the reaction of 1 μmol of substrate per minute under specified conditions of temperature, pH, substrates, and activators.

Answer 34

``` international unit (IU) ```

Question 35

specific. Enzyme concentration is usually expressed in units per liter (IU/L). The unit of enzyme activity recognized by the International System of Units (Système International d'Unités [SI]) is the

Answer 35

katal (mol/s).

Question 36

are chemically bonded to adsorbents, such as agarose | or certain types of cellulose, by azide groups, diazo, and triazine.

Answer 36

Immobilized enzymes

Question 37

widely distributed in tissue, with highest activities found in skeletal muscle, heart muscle, and brain tissue.

Answer 37

CK

Question 38

Total serum CK levels have also been used as an early diagnostic tool to identify patients with_____ infections.

Answer 38

Vibrio vulnificus

Question 39

useful in the diagnosis of ectopic pregnancies.

Answer 39

and | CK/progesterone ratio

Question 40

The major isoenzyme in the sera of healthy people is the

Answer 40

MM form.

Question 41

<6% of total CK

Answer 41

CK-MB

Question 42

atypical forms are | generally of two types (CK)

Answer 42

macro-CK and mitochondrial CK.

Question 43

appears to migrate to a position midway between CK-MM and CK-MB. comprises CK-BB complexed with immunoglobulin.

Answer 43

macro-CK

Question 44

bound to the exterior surface of the inner mitochondrial membranes of muscle, brain, and liver. It migrates to a point cathodal to CK-MM and exists as a dimeric molecule of two identical subunits.

Answer 44

Mitochondrial CK (CK-Mi)

Question 45

is an enzyme released from erythrocytes in hemolyzed samples and appearing as a band cathodal to CK- MM.

Answer 45

adenylate kinase (AK).

Question 46

the most | commonly performed method in the clinical laboratory for CK

Answer 46

Oliver-Rosalki (reverse method)

Question 47

enzyme that catalyzes the interconversion of lactic and pyruvic acids.

Answer 47

Lactate Dehydrogenase

Question 48

occur most frequently with pulmonary | involvement and are also observed in patients with various carcinomas.

Answer 48

Elevations of LDH-3

Question 49

isoenzymes are found primarily in liver and skeletal muscle | tissue

Answer 49

LDH-4 and LDH-5

Question 50

functions as a coenzyme in SGOT/SGPT

Answer 50

Pyridoxal phosphate (B6)

Question 51

Half-life of AST

Answer 51

16hrs

Question 52

Half-life of ALT

Answer 52

24hrs

Question 53

belongs to a group of enzymes that catalyze the hydrolysis of various phosphomonoesters at an alkaline pH.

Answer 53

Alkaline Phosphatase

Question 54

ALP requires ___ as an activator

Answer 54

Mg2+

Question 55

Migration pattern of ALP: fastest to slowest

Answer 55

Liver Bone Placental Intestine

Question 56

Most heat stable to heat labile

Answer 56

Placental Intestinal Liver Bone

Question 57

Placental ALP will resist heat denaturation at

Answer 57

65°C for 30 minutes.

Question 58

ALP activity is measured | before and after heating the serum at

Answer 58

56°C for 10mins

Question 59

The most frequently seen are the Regan | and Nagao isoenzymes. They have been referred to as

Answer 59

carcinoplacental alkaline | phosphatases

Question 60

migrates to the same position as the bone fraction and is the most heat stable of all ALP isoenzymes, resisting denaturation at 65°C for 30 minutes. Its activity is inhibited by phenylalanine.

Answer 60

Regan isoenzyme

Question 61

may be considered a variant of the Regan isoenzyme. Its electrophoretic, heat stability, and phenylalanine inhibition properties are identical to those of the Regan fraction.

Answer 61

Nagao isoenzyme

Question 62

Nagao also can be inhibited by

Answer 62

L-leucine

Question 63

A continuous monitoring technique based on a method devised by _______ allows calculation of ALP activity based on the molar absorptivity of p-nitrophenol.

Answer 63

Bowers and McComb

Question 64

ALP Activity in serum increases approximately _____ on standing at 25°C or 4°C for several hours.

Answer 64

3% | to 10%

Question 65

ALP Values | may be ___ higher following ingestion of a high-fat meal.

Answer 65

25%

Question 66

3 approaches to identify ALP isoenzymes

Answer 66

Electrophoresis Heat Inactivation Chemical inhibition

Question 67

One of the most specific substrates for prostatic ACP is

Answer 67

thymolphthalein | monophosphate.

Question 68

Chemical inhibition methods used to differentiate the prostatic portion most frequently use ____ as the inhibitor.

Answer 68

tartrate

Question 69

Vaginal washings are examined for seminal fluid–ACP | activity, which can persist for up to __ days

Answer 69

4

Question 70

includes incubation with an antibody to | prostatic ACP followed by washing and incubation with p-nitrophenylphosphate.

Answer 70

immunoenzymatic assay (Tandem E)

Question 71

Serum activity decreases within ____ if the sample is left at room temperature without the addition of a preservative.

Answer 71

1 to 2 hours

Question 72

If not assayed immediately, serum should | be

Answer 72

frozen or acidified (<6.5)

Question 73

involved in peptide and protein synthesis, regulation of tissue glutathione levels, and the transport of amino acids across cell membranes.

Answer 73

GGT

Question 74

GGT levels will be increased in patients receiving enzyme- | inducing drugs such as

Answer 74

warfarin, phenobarbital, and phenytoin.

Question 75

TRUE/FALSE: GGT Levels usually return to normal within 2 to 3 weeks after cessation but can rise again if alcohol consumption is resumed.

Answer 75

TRUE

Question 76

most widely accepted substrate for use in GGT analysis is

Answer 76

γ-glutamyl-p- | nitroanilide.

Question 77

TRUE/FALSE: Hemolysis does not interfere with GGT levels because the enzyme is lacking in erythrocytes.

Answer 77

TRUE

Question 78

``` an enzyme belonging to the class of hydrolases that catalyze the breakdown of starch and glycogen. ```

Answer 78

Amylase (AMY)

Question 79

condition that results when the AMY molecule combines with immunoglobulins to form a complex that is too large to be filtered across the glomerulus.

Answer 79

Macroamylasemia

Question 80

2 major bands of amylase

Answer 80

P-type and S-type isoamylase

Question 81

derived from pancreatic tissue;

Answer 81

P isoamylase

Question 82

derived from salivary gland tissue, as well as the fallopian tube and lung.

Answer 82

S isoamylase

Question 83

TRUE/FALSE: The isoenzymes of salivary origin (S1, S2, S3) migrate most quickly, whereas those of pancreatic origin (P1, P2, P3) are slower.

Answer 83

TRUE

Question 84

The most commonly observed fractions of amylase are

Answer 84

P2, S1, and S2.

Question 85

Amylase methodologies: Measures the disappearance of starch substrate

Answer 85

Amyloclastic

Question 86

Amylase methodologies: Measures the appearance of the product

Answer 86

Saccharogenic

Question 87

Amylase methodologies: Measures the increasing color from production of product coupled with a chromogenic dye

Answer 87

Chromogenic

Question 88

Amylase methodologies: Coupling of several enzyme systems to monitor amylase activity

Answer 88

Continuous monitoring

Question 89

TRUE/FALSE: plasma triglycerides suppress or inhibit serum AMY activity, AMY values may be normal in acute pancreatitis with hyperlipemia.

Answer 89

TRUE

Question 90

enzyme that hydrolyzes the ester linkages of fats to produce | alcohols and fatty acids.

Answer 90

Lipase (LPS)

Question 91

used an olive oil substrate and measured the liberated fatty acids by titration after a 24-hour incubation.

Answer 91

Cherry-Crandall | method

Question 92

an oxidoreductase that catalyzes the oxidation of glucose-6-phosphate to 6-phosphogluconate or the corresponding lactone.

Answer 92

Glucose-6-phosphate dehydrogenase (G-6-PD)

Question 93

ACP, | ALP, ALT, amylase, AST, CK, GGT, LDH, lipase

Answer 93

Macroenzymes

Question 94

are high-molecular-mass forms of the serum enzymes that can be bound to either an immunoglobulin (macroenzyme type 1) or a nonimmunoglobulin substance (macroenzyme type 2).

Answer 94

Macroenzymes

Question 95

superfamily of isoenzymes that are involved in the | metabolism of more than 50% of all drugs.

Answer 95

450 enzymes