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Medical Biochemistry > Enzymes/Coenzymes/Inhibitors/Activators > Flashcards

Enzymes/Coenzymes/Inhibitors/Activators Flashcards

0
Q

Other name for Acetyl CoA

A

Pantothenic Acid

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1
Q

Hydrophilic carboxyl group of Facid. Ionized at what pH

A

pH 7

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2
Q

Substrates/Products Citrate Synthase

A

Substrate: OAA + Acetyl Coa
Products: Citrate & Coa

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3
Q

Substrate/Products/Coenzymes ATP-citrate lyase

A

Substrate: Citrate & ATP & Coa
Products: OAA & Acetyl Coa & ADP+Pi

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4
Q

Prosthetic of ACC

A

Biotin. & Adds CO2 to methyl end of Acetyl CoA

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5
Q

Acetyl Coa Carboxylase: Substrate/Products

A

Substrate: Acetyl Coa & ATP & Co2
Products: Malonyl & ADP + Pi

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6
Q

Short-term allosteric regulation of acetyl CoA carboxylase

A

Citrate shifts the polymer - dimer equilibrium towards polymer formation. Activation

Palmitoyl CoA shifts the equilibrium towards dimer formation. Inhibition

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7
Q

Short-term hormonal regulation of acetyl CoA carboxylase

A

Glucagon, epinephrine, and norepinephrine trigger a cAMP dependent phosphorylation of the enzyme (through activation of AMPK) that shifts the equilibrium towards dimer formation (inactive form).

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8
Q

Long-term regulation of acetyl CoA carboxylase

A
  • high carbohydrate and fat-free diets lead to increased synthesis of ACC (up-regulation, induction) resulting in increased synthesis of FA
  • high-fat diets, fasting and glucagon lead to decreased synthesis (down-regulation, repression) resulting in decreased synthesis of FA
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9
Q

Enzyme the hydrolyse Palmitoyl-ACP in order to form free Palmitoyl

A

Thioesterase

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10
Q

Activation Fatty Acid: Substrates, Products, Enzymes

A

Substrates: Fatty Acid + CoASH + 2ATPs
Enzyme: Fatty Acyl Coa Synthetase
Products: Fatty Acyl Coa + AMP + PPi(–>2Pi)

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11
Q

Systemic fatty acid oxidation disorders

Organs, Symptoms, Causes

A

Organs: Liver, Muscle
Symptoms: Hypoglycemia, Hypoketosis
Cause: MCAD deficiency, Carnitine deficiency, CPT-1 deficiency(liver isozyme), Jamaican vomiting sickness

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12
Q

Myopathies fatty acid oxidation disorders

Organs, Symptoms, Cause

A

Organs: Muscle cardiac & skeletal
Symptoms: Muscle cramps during exercise
Cause: Myopathic Carnitine deficiency, CPT-2 deficiency

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13
Q

RLE of Cholesterol Synthesis

A

HMG CoA Reductase

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14
Q

HMG CoA Reductase: Substrate/Products

A

Substrate: HMG CoA (6C) + 2NADPH
Products: Mevalonate (6C) + 2NADP+ + CoA

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15
Q

Inhibitors/Activators HMG Coa Reductase

A

Inhibitors:
Glucagon
Cholesterol
Statin Drugs: Zocor, Lipitor

Activators: Insulin

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16
Q

How does AMP Kinase regulate HMG CoA Reductase

A

• Sterol-Independent Regulation of HMG- CoA Reductase
• High intracellular concentrations of AMP stimulate AMP Kinase which phosphorylates HMG-CoA and inactivates it
• Dephosphorylation by a phosphoprotein phosphatase (activated by insulin) activates HMG –CoA

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17
Q

Upregulation of HMG CoA reductase?

A
  • The amount of HMG CoA reductase enzyme is regulated by intracellular (cytosolic) concentrations of Cholesterol
  • Low cholestrol stimulates the release of a
    regulatory (SREBP) protein from the ER
  • Sterol regulatory element binding protein
    (SREBP) binds to a region in the HMG CoA reductase gene called sterol responsive element (SRE) resulting in increased transcription of the HMG CoA reductase gene and subsequent increase in the amount of HMG CoA reductase.
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18
Q

When does proteolysis of cholesterol occur?

A

High Intracellular cholesterol and/or Mevalonate leads to rapid proteolysis of HMG CoA Reductase enzyme by the ubiquitin system in proteosomes.

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19
Q

SLOS (Smith-Lemli-Opitz Syndrome)

A

A genetic defect of cholesterol synthesis (autosomal recessive)
7-dehydroxycholesterol Reductase, needed for double bond formation in the ring B, is deficient.

Relatively common, leads to microencephaly and other embryological malformations, surviving children have an IQ 20-40

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20
Q

Synthesis of palmitate from Acetyl CoA requires how many ATP and NADHs

A

14 NADPHs & 7 ATPs

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21
Q

Sequence of synthesis of TAGs (Liver & Adipose tissue)

A

DHAP Glycerol phosphate Lysophosphatidic acid Phosphatidic acid(DAG phosphate) Diacylglycerol(DAG) Triacylglycerol (TAG)

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22
Q

Activation Facid(Cytosol): Enzyme/Substrate/Products

A

Enzyme: Fatty Acyl CoA synthetase
Substrate: Fatty acid + CoASH + 2ATP
Products: Fatty Acyl Coa + AMP + PPi

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23
Q

Synthesis of palmitate from Acetyl CoA requires how many ATP and NADHs

A

14 NADPHs & 7 ATPs

24
Q

Sequence of synthesis of TAGs (Liver & Adipose tissue)

A

DHAP Glycerol phosphate Lysophosphatidic acid Phosphatidic acid(DAG phosphate) Diacylglycerol(DAG) Triacylglycerol (TAG)

25
Q

Coenzyme of Propionyl CoA Carboxylase?

26
Q

Coenzyme for Methylmalonyl Coa mutase?

27
Q

Enzyme to form & store cholesteryl esters?

28
Q

Enzymes cleaves TAGs in Chylomicrons & VLDL

A

Lipoprotein lipase

29
Q

Proteins that anchor and activate Lipoprotein Lipase

A

Anchor: Heparan sulfates
Activates: Apo C2

30
Q

Stimulates & Inhibits the reaction: LDL—> OxLDL

A

Stimulators:Superoxide, NO, Hydrogen peroxide, Other oxidants
Inhibitors: Vit E, Ascorbic acid, B-carotene, other antioxidants.

31
Q

Role CETP (cholesteryl ester transfer protein)

A

Allows transfer the transfer of TAGs from VLDL into HDL in exchange for cholesteryl esters

32
Q

What’s so special with HDL

A
  • Potential anti-atherogenic properties
    • Reverse cholesterol transport using as key players apo A-1, LCAT, plasma membrane ABC-transporter for free cholesterol and CETP
    • Contains enzymes that reduce LDL oxidation (Paraoxonase and PAF acetylhydrolase)
  • Potential plaque stabilization properties
    • HDL-mediated cholesterol efflux reduces
      plaque lipid content
    • HDL may reduce plaque macrophage
      content and their activity and increase plaque smooth muscle content and prevent rupture
33
Q

Malicious Enzyme: Substrates, Products

A

Substrate: Malate, NADP+
Products: Pyruvate, NADPH + H+

34
Q

Thioesterase: Substrates, Products

A

Substrates: Palmitoyl-ACP + H2O
Products: Palmitate + ACP-SH

35
Q

Required to produce TAG from 2-Monocylglycerol

A

2 Acyl CoA:monoacylglycerol acyltransferase

& 2 Fatty Acyl-CoA

36
Q

Cholesterol —> Cholic Acid
Enzyme?
Inhibitor/Activator?

A

Cholesterol 7-alpha-hydroxylase (catalyze a the addition of OH group to C-7)
Activator: Cholesterol
Inhibitor: Cholic Acid

37
Q

Coenzyme for Lead

38
Q

Ribose 5-P—-> 5-Phosphoribosyl 1 Pyrophosphate (PRPP)

Enzyme, Cofactor, activator/inhibitor

A

PRPP Synthetase
Cofactors: ATP—> AMP & Mg2+
Activator: Pi
Inhibitor: Purine nucleotides

39
Q

Committed step of nucleotide synthesis: Enz, Substrate, Products, Cofactors, Activators, Inhibitors

A

Enz: Glutamine Phosphoribosyl Pyrophosphate Amidotransferase
Substrate: 5 Phosphoribosyl 1 Pyrophosphate + Glutamine
Products: 5 Phosphoribosylamine + Glutamate
Cofactors: Mg2+
Activator: PRPP
Inhibitors: AMP, GMP, IMP

40
Q

Pteridine Precursor + Aminobenzoic Acid (PABA) —-> Folic Acid

Enzyme, Cofactor, Drug that inhibits

A

EnzyMe: Dihydropteroate Synthetase
Co-factor: ATP, Glutamate
Drug: Sulfonamide

41
Q

Dihydrofolate reductase

Substrate/Product, Cofactor, Inhibitor

A

Substrate: Folic Acid
Product: THF acid
Co-factor: 2NADPH
Inhibitor: Methotrexate

42
Q

Serine hydroxymethyltransferase

Substrate, Product, Cofactor

A

Substrate: Serine
Product: Glycine
Co-factor: THF—> N5,N10 Methylenetretrahydrofolate

43
Q

Enzymes that transport bilirubin in liver

A
  • Ligand protein

- Z protein

44
Q

Synthesis of CTP from UTP

Substrate, Products, enzymes, cofactors

A

Substrate: UTP
Product: CTP
Enzyme: CTP synthase
Cofactor: Glutamine + ATP

45
Q

Ribonucleotide—-> Deoxyribonucleotides

Enzyme, activator, inhibitor

A

Enz: Ribonucleotide di phosphate Reductase
Activator: ATP
Inhibitors: dATP, hydroxyurea

46
Q

Enzyme salvages pyrimidines

A

Pyrimidine Phosphoribosylthransferase

PRPP is the source of ribose phosphate

47
Q

Which Prostaglandins are Mediators of Inflammation

A

PGE2

PGF2a

48
Q

Precursor for Arachidonic acid

A

Linolenic acid

50
Q

Eicosapentanoic acid #

A

20:5 w3

PG and TX from Omega3

51
Q

Reaction catalyzed by Adenosine Deaminase

A

Adenosine—-> Inosine

Release NH3

52
Q

Reactions catalyzed by Purine nucleoside Phosphorylase

A

Inosine—-> Hypoxanthine

Guanosine—-> Guanine

53
Q

What stimulates Tissue factor pathway inhibitor TFPI

& what is its function?

A
  • Heparin

- Bind and inhibit Factor Xa & Factor VIIa/tissue factor

54
Q

Which is administered first: Warfarin or heparin

A

Heparin because warfarin is slow acting.

55
Q

What enzyme oxidized cystein to taurine

A

Cysteine di oxygenate

56
Q

How much ATP required in Purine synthesis?

57
Q

Cholesterol modified by bacteria in intestine to form:

A

Coprostanol & Cholestanol

58
Q

What increases in Acute Hepatitis and long standing hepatitis?

A

Acute: ALT level»>AST levels

Long standing alcohol cirrhosis: AST»>ALT (AST:ALT ratio approx 2:1)

Medical Biochemistry (8 decks)

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