Enzymes

Question 1

enzyme

Answer 1

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

Question 2

activation energy

Answer 2

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

Question 3

apoenzyme

Answer 3

enzyme portion of holoenzyme (missing cofactor)

Question 4

coenzyme

Answer 4

organic cofactor, such as NAD

Question 5

cofactor

Answer 5

non-protein molecule necessary for an enzyme to be active

Question 6

holoenzyme

Answer 6

complete and active system of enzyme and cofactor

Question 7

enzyme-substrate complex

Answer 7

physical binding of a substrate to the active site of an enzyme

Question 8

first order kinetics

Answer 8

reaction rate (binding of substrate to enzyme) is directly proportional to substrate concentration.

Question 9

prosthetic group

Answer 9

coenzyme that is bound tightly to a enzyme

Question 10

international unit

Answer 10

IU; amount of enzyme that will catalyze the reaction of 1 umol of substrate per minute under specified conditions

Question 11

hydrolases

Answer 11

catalyze hydrolysis of various bonds

Question 12

lyases

Answer 12

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

Question 13

isomerases

Answer 13

any one of a class of enzymes that catalyze reactions involving a structural rearrangement of a molecule

Question 14

kinetic assays

Answer 14

continuous monitoring; multiple measurements are made during the reaction, either at specific time intervals or continuously

Question 15

LDH flipped pattern

Answer 15

An inversion of the ratio of LD isoenzymes LD1 and LD2; LD1 is a tetramer of 4 H–heart subunits, and is the predominant cardiac LD isoenzyme; it migrates more rapidly at pH of 8.6 than LD5, normally the LD1 peak is less than that of the LD2, a ratio that is inverted–flipped in 80% of AMIs within the first 48 hrs DiffDx LD flips also occur in renal infarcts, hemolysis, hypothyroidism, and gastric CA, and hemolyzed samples; LDH1 > LDH2

Question 16

Michaelis-menten constant

Answer 16

Km; The relationship between rate of reaction and concentration of substrate depends on the affinity of the enzyme for its substrate; inverse measurement of affinity

Question 17

ligases

Answer 17

catalyze the joining of two substrate molecules, coupled with breaking of the pyrophosphate bond in ATP or similar compound

Question 18

zymogen

Answer 18

an inactive substance which is converted into an enzyme when activated by another enzyme.

Question 19

noncompetitive inhibition

Answer 19

binding an enzyme at a place other than the active site and may be reversible or irreversible; slow rate of reaction; maximum velocity cannot be achieved

Question 20

uncompetitive inhibition

Answer 20

inhibitor bind to the ES complex which will not yield product;

Question 21

mixed inhibitor

Answer 21

binds E or ES complex at a different site from the active site

Question 22

uncompetitive inhibition

Answer 22

inhibitor bind to the ES complex which will not yield product; increasing substrate increases inhibition

Question 23

mixed inhibitor

Answer 23

binds E or ES complex at a different site from the active site

Question 24

Immobilized enzymes

Answer 24

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

Question 25

Immobilized enzymes

Answer 25

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

Question 26

Creatine Kinase

Answer 26

predominant physiologic function occurs in muscle cells, where it is involved in the storage of high-energy creatine phosphate; CK levels are elevated in disorders of cardiac and skeletal muscle (myocardial infarction, rhabdomyolysis, and muscular dystrophy); extreme elevations are seen in Duchenne type muscular dystrophy

Question 27

Lactate Dehydrogenase

Answer 27

enzyme that catalyzes the interconversion of lactic and pyruvic acids; hydrogen transfer enzyme; increased levels are found in cardiac, hepatic, skeletal, and renal disorders;

Question 28

LDH-1

Answer 28

migrates fastest towards anode; HHHH designation; second most isoenzyme (14-26% of LDH); heart and red blood cells; Myocardial infarction, hemolytic anemia

Question 29

LDH-2

Answer 29

major isoenzyme fraction; (29-39% of LDH); HHHM designation; heart and red blood cells; megaloblastic anemia, acute renal infarction, hemolyzed specimen

Question 30

LDH-3

Answer 30

20-26% of LDH; HHMM designation; lung, lymphocytes, spleen, and pancreas; pulmonary embolism, pulmonary pneumonia, lymphocytosis, acute pancreatitis, carcinoma

Question 31

LDH-4

Answer 31

8-16% of LDH; HMMM designation; liver; hepatic injury or inflammation

Question 32

LDH-5

Answer 32

6-16 % of LDH, MMMM designation; skeletal muscle; skeletal muscle injury, muscular dystrophy

Question 33

LDH-6

Answer 33

alcohol dehydrogenase; arteriosclerotic cardiovascular failure; signifies grave prognosis

Question 34

LDH immunoglobulin complexes

Answer 34

LDH complexed with IgA and IgG usually migrates between LDH-3 and -4; not clinically significant

Question 35

Aspartate Aminotransferase (AST)

Answer 35

transaminase- transfer of an amino group between aspartate and alpha-keto acids; also known as serum glutamic-oxaloacetic transaminase (SGOT or GOT); pyridoxal phosphate is a co-enzyme; used to diagnose hepatocellular disorders (i.e. viral hepatitis) and skeletal muscle involvement; in AMI levels rise within 6 to 8 hours and peak at 24 hours and return to normal within 5 days

Question 36

Alanine Aminotransferase (ALT)

Answer 36

catalyzes the transfer of an amino group from alanine to alpha-ketoglutarate with the formation of glutamine and pyruvate; pyridoxal phosphate acts as the coenzyme; confined to evaluation of hepatic disorders; used in conjunction with AST to determine source of elevated AST

Question 37

Alkaline Phosphatase (ALP)

Answer 37

catalyzes hydrolysis of various phosphomonoesters at alkaline pH; most useful in hepatobiliary (obstructive) and bone disorders

Question 38

Acid Phosphatase (ACP)

Answer 38

hydrolase that catalyzes the same types of reaction as ALP but at an acid pH; indicator of prostatic cancer; used in the investigation of rape

Question 39

n-glutamylltransferase (GGT)

Answer 39

involved in transfer of the gamma-glutamyl residue from gamma-glutamyl peptides to amino acids, water, and other small peptides; elevated in virtually all hepatobiliary disorders; may indicate alcoholism;

Question 40

Amylase (AMY)

Answer 40

hydrolase that catalyzes breakdown of starch and glycogen; diagnosis of acute pancreatitis;