Lecture 5

Question 1

enzyme inhibitors

Answer 1

• endogenous inhibitors control mechanisms for biological systems (drugs and toxins)

Question 2

irreversible inhibition

Answer 2

inhibitor is covalently linked to enzyme or bound so tightly dissociate from enzyme is very slow

Question 3

reversible inhibition

Answer 3

• rapid binding equilibrium between enzyme and inhibitor
• enzyme activity fully restored when inhibitor is removed

Question 4

what are the two types of reversible inhibitors?

Answer 4

competitive and nonceompetitive

Question 5

examples of irreversible inhibitors

Answer 5

aspirin, nerve gas (DPF)

Question 6

what groups are present on enzymes that can be inhibited by irreversible inhibitors?

Answer 6

seryl hydroxyl groups

Question 7

what effect is there for the inhibition of COX2?

Answer 7

increases rates of heart attack

Question 8

what part of aspirin is inhibited?

Answer 8

COX1 and COX2

Question 9

Reversible competitive inhibitor

Answer 9

resembles the substrate and binds to active site
- completes with normal substrate
- diminishes rate of catalysis by reducing proportion of enzyme molecules that have bound substrate

Question 10

what happens if DPF is inhibited?

Answer 10

leads to paralysis of the muscle
- causes respiratory failure

Question 11

Reversible noncompetitive inhibitors

Answer 11

• binds to site on enzyme other than the active site
• alters the structure of the enzyme
  enzyme still bind substrate in presence of inhibitor but is unable to catalyze reaction

Question 12

how can competitive inhibition be used?

Answer 12

treating forms of intoxication: methanol (confused for alcohol) and ethylene glycol intoxication (antifreeze)

Question 13

what organ metabolizes methanol?

Answer 13

liver and kidney

Question 14

what are some effects of ethylene glycol?

Answer 14

depression of CNS, metabolic acidosis, renal damage, oxalate crystals

Question 15

examples of noncompetitive inhibitors

Answer 15

enzymes with -SH (sulfhydryl) group (silver, lead, mercury), cleating agents

Question 16

hydrolase

Answer 16

enzymes that catalyze hydrolytic cleavage reaction

Question 17

proteases

Answer 17

degrade proteins by hydrolyzing bonds between amino acids

Question 18

nucleases

Answer 18

degrade nucleic acids by hydrolyzing bonds between nucleotides

Question 19

synthtases

Answer 19

synthesize molecules in anabolic reactions by joining two smaller molecules

Question 20

isomerases

Answer 20

catalyze the rearrangement of bonds within a single molecule

Question 21

polymerases

Answer 21

catalyze polymerization reactions in RNA and DNA synthesis

Question 22

oxido-reductases

Answer 22

catalyze oxidation/reduction reactions (oxidase, reductases, dehydrogenases)

Question 23

kinases

Answer 23

catalyzes transfer of a phosphate group from ATP to other molecules

Question 24

phosphatases

Answer 24

catalyze the hydrolytic removal of phosphate groups from molecules

Question 25

ATPases

Answer 25

catalyze the hydrolysis of ATP

Question 26

what regulates enzyme activity?

Answer 26

concentration of enzyme and substrate, temperature, pH, coenzymes, prosthetic groups, cofactors, phosphorylation/dephosphorylation, zymogen activation

Question 27

optimal pH for proteins

Answer 27

between pH 6 and pH 8 (human blood 7.4)

Question 28

what pH does pepsin function at?

Answer 28

pH 2 --> it is a acidic gastric secretion

Question 29

how does pH affect proteins?

Answer 29

- affects the charge - affects binding of substrate to active site - affects catalytic mechanism of enzyme itself

Question 30

cofactor

Answer 30

- inorganic ions or low-molecular weight organic (nonprotein) or metalloorganic molecules - bind through non-covalent interactions

Question 31

how are prosthetic groups linked?

Answer 31

bound to enzymes by covalent linkages (tightly attached)

Question 32

metal cofactors

Answer 32

- metal ions which can serve as electron pair acceptors - form coordination bonds with enzymes that help properly position reactive groups during catalysis

Question 33

what is phosphorylation?

Answer 33

addition of phosphate group to the side-chain hydroxyl groups of serine, theronine and tyrosine residues

Question 34

how does phosphorylation affect enzyme activity?

Answer 34

depending on enzyme, phosphorylation can increase or decrease enzyme activity

Question 35

what is a zymogen?

Answer 35

inactive precursor of enzymes

Question 36

how are zymogens activated?

Answer 36

proteolytic cleavage of covalent bonds within precursor sequence

Question 37

what enzymes are synthesized as zymogens?

Answer 37

digestive enzymes --> made in the stomach and pancreas

Question 38

what enzyme produces trypsin?

Answer 38

trypsinogen --> cleavage by enzyme enteropeptidase

Question 39

where is enteropeptidase located?

Answer 39

brush border of duodenal mucosa

Question 40

pancreatic proteases are synthesized as inactive zymogens (T/F)

Answer 40

T

Question 41

how does the pancreas protect itself from enzymes?

Answer 41

- zymogens packaged in lipid membrane bounded by secretory granules - potent trypsin inhibitor, binds to active site of trypsin, blocking activity

Question 42

acute pancreatitis

Answer 42

premature activation of the proteolytic and lipolytic enzymes of pancreas --> leads to destruction of pancreas

Question 43

where are lysozymes found?

Answer 43

enzyme found in egg white, saliva, tears and other secretions

Question 44

what does lysozyme do?

Answer 44

catalyzes the cutting of polysaccharide chains in cell walls of bacteria

Question 45

what is creatine kinase associated with?

Answer 45

ATP regeneration in contractile or transport systems

Question 46

what is the function of creatine kinase?

Answer 46

storage of high energy creatine phosphate in muscle

Question 47

where is creatine kinase found?

Answer 47

skeletal muscle, heart muscle and brain

Question 48

what are the three major forms of creatine kinase isoenzymes?

Answer 48

CK-BB (brain type --> brain and other tissue) CK-MM (muscle type --> heart and skeletal muscle CK-MB (hybrid type--> heart and small amount in skeletal muscle)

Question 49

what diseases are associated with high creatine kinase levels?

Answer 49

acute myocardial infarction (AMI), muscular dystrophy, hypothyroidism

Question 50

what disease does elevated serum CK-MM indicate?

Answer 50

skeletal or cardiac muscle injury --> strenuous physical activity or intramuscular injections

Question 51

what disease does elevated serum CK-BB indicate?

Answer 51

damage to CNS, tumors, childbirth

Question 52

which creatine kinase isoenzyme is the major form in serum?

Answer 52

CK-MM: makes up 94-100%