L6- Regulation of enzyme activity

Question 1

explain what’s meant by Zymogen Activity.

Answer 1

they are a group of enzymes that are secreted in an inactive form and later on activated when requires they are called “zymogens” or “proenzymes”

Question 2

how are zymogens activated and is it reversible or not?

Answer 2

they are activated by the hydrolysis of specific peptide bonds at the site of reaction. and its an irreversible process.

Question 3

Give 2 types of enzymes that are form the zymogen group.

Answer 3

Digestive enzymes and blood coagulation enzyme.

Question 4

why is the zymogen activity important?

Answer 4

because its a protective mechanism to prevent auto digestion of tissue secreting digestive enzymes and prevent intravascular coagulation of blood vessels.

Question 5

explain the covalent modification of enzymes.

Answer 5

These group of enzymes are activated by addition of phosphate group (Phosphorylation) and deactivated by the removal of phosphate group (dephosphorylation) and vice versa.

Question 6

explain the allosteric modulation.

Answer 6

these group of enzymes bind to small molecules called Effectors they bind with the enzyme at the allosteric site

Question 7

what are the 2 types of effectors?

Answer 7

positive effectors that increase the catalytic activity

and negative effectors that decrease the catalytic activity.

Question 8

explain the feedback inhibition.

Answer 8

that’s an allosteric regulation where the end product inhibits the enzymatic activity. this regulation occurs at the committed step enzyme.

Question 9

what is the committed step enzyme?

Answer 9

the first irreversible enzyme reaction in a unique pathway.

Question 10

how can cells regulate enzyme activity?

Answer 10

by regulation the enzyme synthesis and controlling the amount of enzyme produced.
inducers are substance that increase the rate of expression of genes coding for enzymes and repressors do the opposite.

Question 11

what are inhibitors?

Answer 11

they are substances that are able to decrease the rate of enzymatic activity.

Question 12

explain the competitive inhibition mechanism.

Answer 12

they are inhibitors that bind to the active site of the enzyme and they are structurally similar to the substrate. they do not produce a product upon forming enzyme-inhibitor complex but rather decrease the rates of reaction. when substrate concentration increases the enzymatic activity increases

Question 13

statin drugs?

Answer 13

they competitively inhibit the rate limiting step in cholesterol biosynthesis as they are structurally similar to natural substrate for this enzyme.

Question 14

explain the noncompetitive inhibition mechanism.

Answer 14

the inhibitors of this type bind with enzyme but not at the active site and lead to conformational changes of the enzymes structure and causes reversible inhibition of the catalytic activity of the enzyme. these inhibitors are structurally not similar to the substrate and enzymatic activity is not reversed when the concentration of substrate is increased.

Question 15

how does non competitive inhibition affect the Vmax and Km of enzyme?

Answer 15

it decreases the Vmax but do not affect the km because they donot interfere in the formation of enzyme-substrate complex.

Question 16

CLINICAL IMPLICATIONS: what’s the relation between lead and noncompetitive inhibitors?

Answer 16

lead may non-competitevly inhibit the rate of reaction of important enzymes in the heam synthesis pathway leading to anemia. Vitamin C and E regain the enzymatic activity. Therefore, they are prescribed to people that work in factories and living in highly polluted areas

Question 17

explain the irreversible inhibition mechanism.

Answer 17

they covalently, tightly and irreversibly bind with the functional group of the enzyme and destroys it. this inhibition decreases the Vmax and doesn’t affect the Km. the inhibitor and substate do not compete because they are not structurally similar.

Question 18

what’s meant by enzyme poison?

Answer 18

substance that when present in any concentration destroys the enzyme.

Question 19

what are ORGANOPHOSPHATES?

Answer 19

they are substances present in pesticides, they contain cholinesterase enzyme that breaks down the neurotransmitter acetylcholine, when accidentally inhaled or ingested causes disruption in nerve signals in the body

Question 20

CYNAIDE?

Answer 20

causes irreversible inhibition of enzymes responsible for synthesize of ATP therefore low doses of cynaide are responsible for some side effects of smoking

Question 21

name the 2 types of plasma proteins

Answer 21

functional and non-functional plasma proteins.

Question 22

what are functional plasma proteins?

Answer 22

they are small group of enzymes secreted by specific organs and have a specific function like the liver secretes zymogens involved in the blood coagulation cascade

Question 23

what are non-functional plasma proteins?

Answer 23

they large enzyme species secreted by the cell during normal cell turnover, they are normally intracellular enzymes and have no physiological function in the plasma

Question 24

How are non-functional plasma proteins used in diagnosis of diseases?

Answer 24

Many disease that cause tissue damage result in an increases secretion of intracellular enzymes in the plasma and it correlates the extent of tissue damage.

Question 25

ALANINE AMINOTRANSFERASE?

Answer 25

its an enzyme abundant in the liver but when high levels of ALT is found in the plasma it signifies damage to the hepatic tissue.

Question 26

ALKALINE PHOSPHATASE?

Answer 26

its an enzyme that increases in the plasma when there is a bone disease like osteoporosis, rickets and bone tumors.

Question 27

give 2 examples of enzymes used in treatment of disease.

Answer 27

1- digestive enzymes are prescribed for people experiencing maldigestion
2- Alteplase help in treatment of myocardial infractions by enhancing the activation of enzymes needed for degradation of thrombus