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Biochem > Lecture 3 -Enzymes > Flashcards

Lecture 3 -Enzymes Flashcards

1
Q

Oxioreductases

A

Oxidation-reduction reactions

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2
Q

Transferases

A

Transfer of C, N, or P containing groups

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3
Q

Hydrolases

A

Cleavage of bonds by addition of water

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4
Q

Isomerases

A

Racemization of optical or geometric isomers

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5
Q

Ligases

A

Formation of bonds between carbon and O, S, N coupled to hydrolysis of high energy phosphates

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6
Q

Lyases

A

Cleavage of C-C, C-O, and C-S and certain C-N bonds

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7
Q

Isoenzymes

A

Different enzymes that catalyze same reaction, usually in different tissues
-hexokinase/glucokinase -lactate dehydrogenase -creatine kinase

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8
Q

Proenzyme/Zymogen

A

Inactive enzymes w extra protein sequence activated by cleavage of of protein synthesis
-Digestive proteases -Blood coagulation enzymes

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9
Q

Apoenzyme

A

Inactive form of enzyme

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10
Q

Holoenzyme

A

Active form, enzyme + cofactor

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11
Q

Cofactor Types

A

Metal ions: -Bind substrate or participate in oxidation-reduction
-Small orgnic molecules (coenzyme): -Transfer of chemical groups or oxidation-reduction (usually enzymes)

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12
Q

Vmax

A
  • Theoretical maximum velocity
  • Directionally proportional w enzyme concentration
  • 1/Vmax is Y intercept on linearized Michaelis-Menten equation (small y-intercept = large Vmax)
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13
Q

Km

A
  • Substrate concentration that permits reaction velocity of Vmax/2
  • Inversely related to affinity of enzyme for substrate (high Km=low affinity, low Km = high affinity
  • 1/Km is X-intercept on linearized plot (small x intecept = large Km = low affinity)
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14
Q

Product Inhibition

A

Product of enzymatic reaction is an inhibitor of the enzyme, regulates own synthesis
-Heme

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15
Q

Allosteric Regulation

A

Regulators bind outside of active site and cause conformational change that alter enzyme activity positively or negatively
-Can change Vmax or Km

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16
Q

Homotropic Effector

A
  • Substrate itself is allosteric effector in multisubunit enzyme
  • Binding of substrate to one subunit changes binding of substrate to other units (ex. Binding of O2 to hemoglobin increases affinity)
  • Changes shape of curve
17
Q

Heterotropic Effector

A
  • Allosteric effector is different from substrate
  • Doesnt compete for active site (Ex. 2,3-BPG decreases O2 affinity, but doesnt bind active site)
  • Changes Km
18
Q

Phospohorylation/dephosphorylation

A

Kinases/phosphotases add/remove phosphate groups to enzymes -Changes enzymatic activity depending on enzyme
-Ex. Gycogen synthase phosphorylated is inhibited, glycogen phosphorylase phosphorylated is activated

19
Q

Proteolytic Processing

A

-Enzymes are produced in proenzyme (inactive) form -Cleavage of proenzyme leaves active form

20
Q

Regulation of Enzyme Levels

A
  • Transcription, translation, degredation of enzyme are regulated
  • Heme
21
Q

Negative Feedback Inhibition

A

End product of pathway regulates first step in pathway

22
Q

Reversible Enzyme Inhibitors

A

Bind non-covalently to enzyme, so can be dissociated from enzyme

  • Competitive
  • Noncompetetive
23
Q

Competetive

A

Inhibitor competes with the substrate at the active site

Drugs: -Statins -Ibuprofen -Catopril

24
Q

Non Competetive

A

Inhibitor does NOT compete w enzyme at active site

25
Q

Irreversible Enzyme Inhibitors

A

Bind very tightly (usually covalently) to active site and prevent substrate binding

  • Transition-state (Active site-directed)
  • Suicide Inhibitors (Enzyme-activated)
26
Q

Transition-state (Active site-directed)

A

Inhibitor (without alteration in its structure) forms covalent linkage w catalytic site
Drugs: -Organophosphates -Aspirin

27
Q

Suicide Inhibitors (Enzyme-activated)

A

Enzyme modifies inhibitor, inhibitor binds very tightly to active site and cant be displaced
Drugs: -Penicillin -Allopurinol

28
Q

AST

A

-Aspartate Aminotransferase
-Aspartate -> glutamate
Tissue: heart, skeletal muscle, liver, brain
Diagnostic Use: liver disease

29
Q

ALT

A

-Alanine Aminotransferase
-Alanine -> glutamate
Tissue:Liver
Diagnostic Use: Liver disease (ALT> AST)

30
Q

Amylase

A

Tissue: Pancreas, Salivary gland

Diagnostic Use: Acute pancreatitis, biliary obstruction

31
Q

CK

A

-Creatine Kinase
Tissue: Skeletal muscle, heart, brain
Diagnostic Use: Muscular dystrophy, MI

32
Q

GGT

A

Tissue: Liver

Diagnostic Use: hepatitis, cirrhosis

33
Q

LDH

A

Tissue: Heart, liver erythrocytes

Diagnostic Use: Lymphoma, hepatitis

34
Q

Lipase

A

Tissue: Pancreas

Diagnostic Use: Acute pancreatitis, biliary obstruction

35
Q

Alkaline Phosphatase

A

Tissue: Osteoblast

Diagnostic Use: bone disease/tumors

36
Q

Acid Phosphatase

A

Tissue: Prostate

Diagnostic Use: Prostate cancer

Biochem (14 decks)

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