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Biochemisty > Fat/Lipid synthesis > Flashcards

Fat/Lipid synthesis Flashcards

1
Q

Linolenic acid structure

A

18:3 (9,12,15)

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2
Q

Arachidonic acid structure

A

20:4 (5,8,11,14)

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3
Q

Triacylglycerol (TAG)

A

-Storage of energy
- Physiological fat
- 1st Carbon: saturated fat
2nd carbon: unsaturated fat
3rd: saturated or unsaturated fat

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4
Q

Acetyl-CoA Carboxylase (ACC)

A

-Fatty acid biosynthesis, cytoplasm
Overall: 7 Acetyl CoA + 7 CO2 + 7 ATP –> 7 Malonyl-CoA + 7 ADP + 7 Pi

  • Synthesis of palmitate
  • Rate-limiting step, irreversible
  • ACC has a biotin arm (attached to biotin carrier protein in ACC through lysine) which uses the energy of the ATP to attach to CO2. Then acetyl CoA nucleophilic attacks CO2 to make malonyl CoA

-regulation
Downregulated by glucagon (PKA), adrenaline (PKA), palmitoyl-COA, AMPK (TAMP)
Upregulated by insulin (PP), citrate
-MalonylCoA inhibits FA transport for degradation

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5
Q

Fatty acid synthase (FAS)

A
  • Fatty acid biosynthesis , cytoplasm
  • (Complex of many enzymatic activities (6)in one protein + an acyl carrier protein ) x2 –> dimer (two multi reaction chamber)

Contains 6 enzymes: MAT, KS, KR, ER, DH, TE

ACP attaches to the PPE part of coenzyme a. It is the SH of PPE that covalently attaches to acetyl CoA

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6
Q

ATP-citrate lyase

A
  • Breakdown of citrate into Acetyl CoA for FA synthesis (only citrate can be transported into the mitochondria)
  • Citrate + CoA + ATP –> OAA + Acetyl-CoA+ ADP + Pi
  • OAA is then transformed into malate. Malate is transformed into pyruvate with malic enzyme. There is production of 1NADPH, and pyruvate an go back into the mitochondria
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7
Q

Biotin carboxylase

A

attached to biotin
- Biotin + CO2 + ATP –> Biotin-CO2 + ADP + Pi.

Then the biotin carrier protein swings the Biotin-CO2 into the transcarboxylase component of ACC

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8
Q

Transcarboxylase

A

Acetyl CoA+ CO2 (from biotin) –> Malonyl CoA

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9
Q

Malonyl-Acetyl-CoA-ACP transacetylase (MAT)

A

1st reaction of FAS for FA synthesis

1- acetyl CoA +ACP-SH –> Acetyl-ACP + CoA-SH

2- Malonyl-CoA + ACP-SH –> Malonyl-ACP + CoA-SH

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10
Q

ß-Ketoacyl-ACP-synthase (KS)

A

2nd step in FAS for FA synthesis

1- acetyl-ACP + KS –> Acetyl-KS + ACP-SH
2- acetyl-KS + malonyl-ACP –> Acetoacetyl-ACP + CO2 + KS

Condensation reaction

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11
Q

ß-ketoacyl-ACP reductase (KR)

A

3rd step of FAS for FA synthesis.

Acetoacetyl-ACP + NADPH + H+ –> D-Hydroxybutyryl-ACP + NADP

reduction step

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12
Q

ß-hydroxyacyl-ACP dehydrase (DH)

A

-4th step in FAS for FA synthesis.

D-ß-Hydroxybutyryl-ACP –> å,ß-trans-butenoyl-ACP + H2O

dehydration step

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13
Q

Enoyl-ACP reductase (ER)

A

å,ß-trans-butenoyl-ACP + NADPH + H+ –> bytyryl-ACP + NADP

reduction step

*use the product 7 times in order to make palmitoyl-ACP

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14
Q

Palmitoylthioesterase (TE)

A

Palmitoyl-acp +water–> palmitate

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15
Q

Overall reqction for palmitate synthesis

A

8 Acetyl CoA

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16
Q

Linoleic acid structure

A

18:2 (9,12)

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17
Q

Overall reaction for palmitate synthesis

A

8Acetyl CoA + 7ATP + 14 NADPH + 14H+–> 6 H2O + 14 NADP + 7ADP + 7 Pi+ palmitate + 8CoA

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18
Q

Thiokinase

A

Palmitate + ATP –” Palmitoyl-CoA (is a thioester)+ AMP + PPi

Can be:

  • Stored as TAG
  • used for energy
  • derivatized: elongated or desaturated
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19
Q

3-ketoacyl-CoA synthase

A

1st reaction in microsomal (Smooth ER) elongation (Major): fatty acid elongation (n+2)

Acyl-CoA (10C and more, sat. or unsat.) + Malonyl CoA –> 3-Ketoacyl-CoA + CoA-SH + CO2

-Condensation reaction.

20
Q

3-Ketoacyl-CoA reductase

A

2nd reaction in microsomal elongation

3-D-Ketoacyl-CoA + NADPH + H+ –>3-Hydroxyacyl-CoA + NADP

-Reduction reaction

21
Q

3-Hydroxyacyl-CoA dehydrase

A

3rd reaction in microsomal elongation

3-Hydroxyacyl-CoA –> 2-trans-enoyl-CoA + H2O

-Dehydration reaction

22
Q

2-trans-enoyl-CoA reductase

A

2-trans-enoyl-CoA + NADPH + H+ –> Acyl-Coa(n+2)

23
Q

thiolase

A

1st step in mitochondrial elongation : fatty acid elongation (Minor pathway)

Acyl-CoA + Acetyl CoA –> ß-ketoacylCoA + CoA-SH

24
Q

3-L-hydroxyacyl-CoA dehydrogenase

A

2nd step in mitochondrial elongation

ß-ketoacyl-CoA + NADH + H+ –> L-ß-hydroxyacyl CoA + NAD

-reduction reaction

25
Q

Enoyl-CoA hydratase

A

3rd step in mitochondrial elongation

L-ß-hydroxyacyl CoA –> a,ß-trans-Enoyl-CoA + H2O

-Dehydration reaction

26
Q

Enoyl-CoA reductase

A

4th step in mitochondrial elongation

a,ß-trans-enoyl-CoA + NADPH + H+ –> Acyl-CoA (n+2) + NADP

-Reduction reaction

27
Q

Generic desaturation of FA in the ER (microsomal)

conditions

A

Humans have 4 desaturases (give e- to form H2O): ∆9,∆6,∆5,∆4 (count carbonyl as C1)

  • y = 7,4,3,2 (must be saturated) (don’t count carbonyl as C1)
  • X > or = 5C (can be sat. or unsat.) (don’t count last CH3*)
  • Spacing between 2 double bonds (n+3)

*for x and y , count only CH2

28
Q

Glycerol-P dehydrogenase

A

1st step TAG synthesis in liver and adipose tissue

-Dihydrocyacetone phosphate + NADH –> Glycerol phosphate

29
Q

Glycerol kinase

A

1st step TAG synthesis in liver only

Glycerol + ATP –> Glycerol phosphate + ADP

30
Q

Acyltransferase

A

2n, 3rd and 5th reaction of TAG synthesis

2nd: Glycerol phosphate + Acyl-CoA (sat.) –> lysophosphatidic acid + CoA-SH
3rd: Lysophosphatidic acid + Acyl-CoA (unsat.) –> phosphatidic acid (DAG phosphate) + CoASH

5th:
Diacylglycero (DAG) + Acyl-CoA –> Triacylglycerol (TAG) + CoA-SH

31
Q

phosphatase

A

4th reaction of TAG synthesis

Phosphatidic acid + H2O –> Diacylglycerol (DAG) + Pi

32
Q

Carnitine palmitoyl-transferase I

A

-Fatty acid transport into mitonchondria matrix

fatty acyl CoA + Carnitine –> fattyacyl-carnitine + CoA

-reaction in imm

33
Q

Carnitine palmitoyl-transferase II

A

-Fatty acid transport into the mitochondrial matrix

fattyacyl-carnitine + CoA –> Fattyacyl-CoA + carnitine

-reaction in matrix

34
Q

fatty acyl CoA synthetase

A

Fatty acid + ATP –> Fatty acyl CoA + AMP + PPi

35
Q

Acyl-CoA dehydrogenase (AD)

A

1st reaction of ß-oxidation of fatty acid (occurs in mitochondria)

Fatty acyl-CoA + FAD –> 2-trans-enoyl-CoA + FADH2

*FADH2 electrons transfered to ETC for production of 2ATP

36
Q

Enoyl-CoA hydratase

A

2nd step in ß-oxidation of fatty acid

2-trans enoyl CoA + H2O –> 3-hydroxyacyl-CoA

37
Q

3-Hydroxyacyl CoA dehydrogenase

A

3rd step in ß-oxidation of fatty acids

3-L-hydroxyacyl-CoA + NAD –> 3-ketoacyl -CoA + NADH + H+

  • NADH later used in ETC: produces 3 ATP
38
Q

ß-ketoacyl CoA thiolase

A

3-ketoacyl-CoA + CoA –> acyl-CoA (n-2) + acetyl-CoA

  • In odd chain FA degradation, the very end product is propionyl CoA (3C)
  • Each acetyl CoA provides 12 ATP through the TCA cycle
39
Q

Summary of the energy yield from the oxidation of palmitoylCoA

A

14 ATP (from 7FADH2) + 21 ATP (from 7NADH2) + 96 ATP (from 8 acetylCoA) = 131 ATP - 2ATP (for palmitate–> palmitoyl CoA) = 129ATP

40
Q

propionyl-CoA carboxylase

A

1st Step for conversion into succinyl-CoA

Propionyl-CoA + HCO3 (biotin) + ATP –> D-Methylmalonyl-CoA + ADP + Pi

41
Q

methylmalonyl-CoA epimerase

A

2nd step for conversion into succnyl-CoA

D-Methylmalonyl-CoA L-methylmalonyl-CoA

42
Q

Methyl-malonyl-CoA mutase

A

3rd step for conversion into succinyl-CoA

L-Methylmalonyl-CoA + coenzyme B12 succinyl-CoA

succinyl CoA later transformed into OAA then glucose.

43
Q

Enoyl-CoA isomerase

A

Degradation of fatty acid with 3,4 C=C bond obstacle
(because only 2,3 trans double bond can be used for ß-oxidation)

3,4 fatty acyl –> 2,3 trans fatty acyl ==> ßoxidation

44
Q

2,4-dienoyl-Coa reductase

A

Degradation of FA with 4,5 C=C bond obstacle

(1st: 4,5 C=C fatty acyl + FAD –> 2,4 dienoyl fatty acid (2 db) + FADH2)
2nd: 2,4 dienoyl fatty acyl + NADPH + H+ –> 2,3enoyl fatty acyl + NADP

45
Q

3,2-enoyl-CoA isomerase

A

3,2-enoyl fattyacyl –> 2,3 trans fattyacyl ==> ß-oxidation

Biochemisty (6 decks)

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