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MCM - Molecular and Cellular Mechanisms) > TBL 2 - Enzyme catalysis, kinetics and regulation > Flashcards

TBL 2 - Enzyme catalysis, kinetics and regulation Flashcards

1
Q

Kinase

A

Transfers phosphate group from high energy molecule to a substrate (ATP hydrolysis)

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2
Q

Phosphorylase

A

Adds inorganic phosphate to a substrate without using ATP

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3
Q

Dehydrogenase

A

Catalyzes oxidation-reduction reaction through the transfer of H

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4
Q

Ligase

A

Binds or adds ligands

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5
Q

Transferase

A

Transfers functional group from one molecule to another

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6
Q

Oxidoreductase

A

Catalyzes oxidation-reduction reaction through the transfer of electrons

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7
Q

Approximation

A

Enzyme brings reactants closer together

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8
Q

Covalent catalysis

A

A reactive group on the enzyme is covalently bonded to substrate

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9
Q

Acid-base catalysis

A

A reactive group on enzyme acts as proton acceptor or donor

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10
Q

Metal ion catalysis

A

Assists in electrophilic or nucelophilic interactions or bonds to the substrate

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11
Q

Transition state inhibitors

A

Drugs that resemble transition state and bind to enzyme

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12
Q

Example of transition state inhibitor

A

Tamiflu inhibits influenza A and B neuraminidase

Pcn inhibits bacterial enzyme glycopeptide transpeptidase

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13
Q

Co-factors

A

Inorganic ions that assist in enzyme catalysis

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14
Q

The binding of a substrate to enzyme results in ____ called ____

A

a release of free energy

binding energy

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15
Q

Co-enzyme

A

Small organic non-protein that assist enzymes

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16
Q

Ex of co-enzyme

A

FAD, NAD, coenzyme A, biotin

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17
Q

Many co-enzymes are a derivative of ____

A

vitamins

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18
Q

THF stands for ____ and is derived from ____ and functions in ____

A

Tetrahydrofolate

Folic acid

Methylation

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19
Q

Co factor ex

A 
Iron (Fe)
Copper (Cu)
Zinc (Zn)
Magnesium (Mg)
Selinium (Se)
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20
Q

Magnesium is often a cofactor for which enzyme category?

A

Kinase

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21
Q

Prosthetic group

A

A non-protein group (organic or inorganic) that forms a covalent bond with a protein

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22
Q

Biotin catalyzes ___ reactions

A

carboxylation

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23
Q

____ is frequently present in enzyme catalysis involving acid-base catalysis

A

Histidine

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24
Q

Histidine has a pKa near ____

A

Physiological pH

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25
Q

Serine proteases

A

Chymotrypsin, trypsin, elastase

Family of enzymes that sequentially cleave peptide bonds between specific AAs

26
Q

Chymotrypsin

A

Cleaves proteins on the carboxyl side of aromatic or large hydrophobic amino acids

Binding pocket lined with AA which have small or no side chains

27
Q

Trypsin

A

Cleave Arg and Lys (postiively charged AA)

Binding pocket has Asp (negatively charged AA)

28
Q

Elastase

A

Cleaves at the C-terminus at AAs with small side chains

Binding pocket lined with bulky AAs

29
Q

Zymogen (proenzyme)

A

Enzyme precursor

30
Q

Isozymes

A

Enzymes that catalyze the same chemical reaction but differ in AA sequence

31
Q

Vmax

A

Reached when enzyme is saturated with substrate

32
Q

Zero order reaction

A

Velocity is independent of [S]

33
Q

First order reaction

A

Velocity is directly proportional to [S]

34
Q

Michaelis-Menten eq

A

V0 = Vmax[S] / Km + [S]

35
Q

Km =

A

Substrate concentration at 1/2 of Vmax

36
Q

Low Km has _____ affinity for [S]

A

high

37
Q

High Km has _____ affinity for [S]

A

low

38
Q

Lineweaver-burk plot equation and interpretation

A

1/V0 = Km/Vmax * 1/[S] + 1/Vmax

y-int = 1/Vmax
x-int = -(1/Km)
slope = Km/Vmax
39
Q

Kcat

A

Turnover number

Vmax/Et = Kcat

40
Q

Catalytic efficency

A

Kcat/Km

Cats are efficient at jumping over the moon

41
Q

Competitive inhibition

A

Km increases
Vmax stays the same
can be overcome by increased substrate

42
Q

Examples of competitive inhibition

A

Methotrexate - dyhydrofolate reducatase
Statins - HMG CoA reductase
Ethanol - alcohol deydrogenase

43
Q

Non competitive inhibition

A

Km stays the same
Vmax goes down

Inhibitor binds at allosteric site causing conformational change

44
Q

Example of Non competitive inhibition

A

Allopurinol - xanthine oxidase

used in gout

45
Q

Uncompetitive inhibition

A

Bind at the enzyme-substrate complex

decreases Km and Vmax

46
Q

Examples of Uncompetitive inhibition

A

Lithium used to treat bipolar disorder

Arsenate

47
Q

Irreversible inhibition

A

permanently inactivate enzyme
Covalently bound
Seen in the use of aspirin which inhibits COX
and ferrochelatase which is inhibited by lead

48
Q

Km =

A

-1/x-intercept

49
Q

Allosteric effector

A

Bind to a site other than active site on enzyme, causing a conformational change in the active site which either promotes or inhibits binding of substrate

50
Q

Allosteric enzymes

A

Change their conformational upon binding of an effector, “cooperative”

51
Q

Example of cooperativity and allosteric interactions

A

Hemoglobin

sigmoidal curve

52
Q

Serine protease “catalytic triad”

A

Histidine, Aspartic acid, Serine

53
Q

Cooperativity

A

BInding of one ligand will increase the affinity for binding another ligand

54
Q

Feed back regulation

A

Positive feedback loop: product upregulates pathway

Negative feedback loop: products down regulates pathway

55
Q

Feed foward regulation

A

Product that regulates an enzyme, which is further ahead of it in pathway

56
Q

Coenzyme TPP helps to transfer _______

A

Aldehyde group

57
Q

Coenzyme biotin helps to transfer _____

A

CO2

58
Q

Coenzyme CoA-SH helps to transfer _____

A

Acyl group

59
Q

Coenzyme NADH helps to transfer _____

A

Hydride group

60
Q 
Metal ion cofactor:
Zn
Mg
Cu
Fe
Se

Which enzymes are they involved in?

A 
Zn- superoxide dismutase
Mg- ATPases, Kinases
Cu- cytochrome c oxidase 
Fe- cytochromes 
Se- glutathione peroxidase

MCM - Molecular and Cellular Mechanisms) (6 decks)

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