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Foundations > Biochemistry- Enzymes/Reactions > Flashcards

Biochemistry- Enzymes/Reactions Flashcards

1
Q

Glycosidase

A

Breaks glycosidic bonds

AKA Glycoside hydrolase

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2
Q

Iduronate sulfutase deficiency

A

Impaired degradation of GAGs (Dermatan sulfate and heparan sulfate affected)

  • Results in Hunter Syndrome (MPS II)
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3
Q

α- L iduronidase deficiency

A

Impaired degradation of GAGs (Dermatan sulfate and heparan sulfate affected)

  • Results in Hurler Syndrome (MPS I)
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4
Q

Sanfilippo syndrome mechanism

A
  • Missing enzyme for one of four steps to remove N-Sulfated/N-acetylated glucosamine residues from HEPARAN SULFATE
Depending on type, missing:
A- Heparan sulfamidase
B- N-acetyl glucosaminidase
C- Glucosamine- N- Accetyl transferase def.
D-  N-acetylglucosamino-6-sulfutase
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5
Q

ß- Glucuronidase definciency

A

Impaired degradation of GAGs (Dermatan sulfate and heparan sulfate affected)

  • Results in Hurler Syndrome (MPS VII)
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6
Q

Lactase deficiency

A
  • Intolerance of ingested milk products (Lactose intolerance)–> diarrhea, bloating, flatulence, increased H2 in breath

Can be congenital or due to intestinal injury

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7
Q

Sucrase-isomaltase deficiency

A

Ingested Sucrose intolerance

  • Impaired split of sucrose, maltose, maltotriose
  • -> diarrhea, bloating, increased H2 in breath
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8
Q

Fructose intolerance

A

Deficiency in GLUT-5

  • Can’t transport/absorb fructose (in large/moderate amounts)
  • GI distress, gas, H2 gas in breath

NOT the same as inability to metabolize fructose

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9
Q

I-cell disease

A

Deficiency in ability to phosphorylate mannose 6 (on a glycoprotein)

  • Glycoprotein can’t mark target enzymes to go to lysosome for destruction, so there is a bulidup of digestive enzymes in the cell
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10
Q

Reaction catalyzed by hexokinase?

- Cofactors/Requirements (if any)?

A

D-Glucose –> Glucose-6-phosphate

Irreversible, Step 1 of Glycolysis

  • NOT in liver/pancreas
  • Requirement: Mg 2+, ATP
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11
Q

Reaction catalyzed by glucokinase?

- Cofactors/Requirements (if any)?

A

D- Glucose –> Glucose-6-phosphate

Irreversible, Step 1 of glycolysis

  • In liver/pancreas ONLY
  • Requirement: Mg 2+, ATP
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12
Q

Reaction catalyzed by phosphofructokinase?

- Cofactors/Requirements (if any)?

A

Fructose-6- Phosphate –> Fructose-1,6-
bisphosphate

Irreversible, Rate limiting, and Committed step of Glycolysis (Step 3)

  • Requirement: Mg 2+, ATP
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13
Q

Reaction catalyzed by Glyceraldehyde 3- Phosphate dehydrogenase?
- Cofactors/requirements?

A

Glyceraldehyde-3-phosphate 1,3-bisphosphoglycerate

Reversible, not regulated (step 6 of glycolysis)

  • First NADH generated (x2)
  • Requirement: NAD+, Pi

Arsenate (arsenic poisoning) affects this step of glycolysis

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14
Q

Reaction catalyzed by Phosphoglycerate kinase?

- Cofactors/requirements?

A

1,3-bisphosphoglycerate 3-phosphogylcerate

Reversible, not regulated (step 7 of glycolysis)

** First substrate level phosphorylation, ATP generated (x2)

  • Requires ADP & Pi, Mg2+
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15
Q

Reaction catalyzed by pyruvate kinase (PK)?

- Cofactors/requirements?

A

Phosphoenolpyruvate –> Pyruvate

  • Irreversible, regulated (step 10 of glycolysis)

**Substrate level phosphorylation, ATP generated (x2)

-Requires: ADP, Pi, Mg2+, K+

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16
Q

How much ATP and NADH is generated during aerobic glycolysis?

A

2 ATP, 2 NADH

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17
Q

Reaction catalyzed by lactate dehydrogenase?

- Cofactors/requirements?

A

Pyruvate –> Lactate (reduction)

  • Last step in anerobic glycolysis

Requires: NADH

Lens/cornea, Kidney medulla, RBCs, testes, leukocytes all rely on anerobic glycolysis

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18
Q

Pasteur effect

A

The slowing of glycolysis in the presence of oxygen (b/c more ATP is produced)
- Glycolysis is faster under aerobic conditions

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19
Q

Reaction catalyzed by Enolase?

- Cofactors/requirements?

A

2-phosphglycerate PEP

Reversible & not regulated, Step 9 in glycolysis

  • Requirement: Mg2+
    Water is eliminated

Fluoride inhibits this enzyme, so bacteria in mouth produce less lactic acid, less cavities

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20
Q

Mechanism of Arsenic poisoning?

A
  • Affects glycolysis and TCA
  • In glycolysis, Arsenate gets incorporated into glyceraldehyde 3-phosphate –> forming 1-Arseno-3-phosphoglycerate
  • Hydrolyses spontaneously/easily to 3-phosphoglycerate b/c unstable
  • Bottomline: NO SUBSTRATE LEVEL PHOSPHORYLATION IN STEP 7, NO ATP GAIN, RBCS SUFFER BECAUSE CANT PRODUCE ATP
  • In the TCA–>
  • Arsenite inhibits enzymes requiring LIPOIC ACID (i.e. PDH, α-ketoglutarate dehydrogenase, branched-chain amino acid α–keto acid dehydrogenase)
    - Arsenite forms a stable complex with the thio group of lipoic acid
  • Affects the brain and cause neurologic disturbance and death
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21
Q

Regulation of glycolysis at step 1?

A

Inhibition:
- Negative feedback of glucose 6- phosphate (ONLY HEXOKINASE, b/c glucokinase has larger Km and less affinity, and larger V max)

Activation (indirect):
- Insulin stimulates GLUT 4 to come to cell membrane from inside cell, so intake of glucose into adipose (ie) cells increases

  • Hexokinase is active at low glucose levels compared to glucokinase
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22
Q

Regulation of glycolysis at step 10?

A

Allosterically activated:
- Fructose 1,6 bisphosphate (in liver, muscle 1&2, RBC by all 4 isozymes)- FEED FORWARD

Inhibition:

  • ATP (allosteric)
  • IN LIVER: glucagon decreases PK (pyruvate kinase) activity by phosphorylation
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23
Q

Regulation of glycolysis at step 3?

A

Activation (allosteric):
- AMP, ADP, Fructose-2,6-bisphosphate
F-2,6-BP is regulated by insulin/glucagon

Inhibition:
- ATP, citrate, high [H+]

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24
Q

Mechanism of Fructose-2,6-bisphosphate?

A
  • A VERY POTENT ACTIVATOR OF PFK-1 (step 3 glycolysis enzyme)
  • Also inhibits gluconeogenesis?

-Production is regulated by tandem enzyme: has Phosphofructokinase-2 (PFK-2) domain
AND Fructose-2,6-bisphosphatase (FBP-2) domain.

** In the presence of Insulin–> phosphotase active–> phosphotase dephosphorylates PFK-2–> PFK-2 (w/ATP) catalyzes phosphorylation from F-6-P to generate F-2,6-BP –> more activation of PFK-1 –>more glycolysis

** In the presence of glucagon –> Protein Kinase A is active –> PKA phosphorylates FBP-2–> FBP-2 removes phosphate from Fructose 2,6-BP (inactivates)–> less activation of PFK-1 –> less glycolysis

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25
Q

Pyruvate kinase deficiency

A
  • RBCs can’t complete glycolysis (b/c need lactate to regenerate NAD+)
  • 50% less ATP produced
  • ATP is not available to regulate ION TRANSPORTERS
  • Hemolytic anemia occurs
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26
Q

Reaction catalyzed by Pyruvate dehydrogenase (PDH) complex?

Requirements?

A

Pyruvate –> Acetyl CoA

Requires:

  • Thiamine pyrophospate (Vitamin B1) - E1 aka Pyruvate DEcarboxylase
  • Lipoic acid- E2
  • CoA- E2
  • FAD- E3
  • NAD- E3

-CO2 is released (lost when TPP binds to pruvate, E1 domain)

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27
Q

What regulates PDH complex? What influences the regulators?

A

Inhibition:
* PDH kinase (inhibits E1, less TCA))

  • ATP, Acetyl CoA, and NADH activate the inhibitor (enough energy, less TCA)
  • Pyruvate INHIBITS the inhibitor (PDH kinase) – not enough energy, more TCA

Activation:
* PDH phosphotase (activates E1)

  • Ca2+ released by skeletal muscle cells during contraction activates activator (need more energy, more TCA)
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28
Q

Reaction catalyzed by citrate synthase?

Requirements?

A

Oxaloacetate –> Citrate (Step 1 of TCA)

Irreversible, regulated

Requires: Acetyl CoA, H2O

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29
Q

Regulation of citrate synthase?

A

Inhibition: Citrate, NADH, Succinyl CoA

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30
Q

What does fluoroacetate inhibit?

A

Fluoroacetate is a rat poison/plant toxin

  • Inhibits Acitonase (Fe-S) enzyme that catalyzes Citrate to Isocitrate reaction (Step 2 of TCA)
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31
Q

Reaction catalyzed by isocitrate dehydrogenase?

Requirements?

A

Isocitrate –> alpha-ketoglutarate (step 3 of TCA)

RATE LIMITING, irreversible, regulated

Requires: NAD+

*1ST NADH YIELD, 1ST CO2 RELEASED

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32
Q

Reaction catalyzed by alpha-ketoglutarate dehydrogenase?

Requirements?

A

alpha-ketoglutarate succinyl CoA (step 4 of TCA)

Requires:

  • Vitamin B1 (thiamine)
  • Lipoic Acid
  • CoA
  • FAD
  • NAD

*2ND NADH YIELD, 2ND CO2 RELEASED

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33
Q

Regulation of Isocitrate dehydrogenase?

A

Activation: ADP, Ca2+ (in muscle)
Inhibition: ATP, NADH

Isocitrate –> alpha-ketoglutarate (step 3 of TCA)

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34
Q

Regulation of alpha-ketoglutarate dehydrogenase?

A

Activation: Ca2+ (muscle)
Inhibition: ATP, NADH, GTP, Succinyl CoA

alpha-ketoglutarate succinyl CoA (step 4 of TCA)

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35
Q

Reaction catalyzed by succinate thiokinase?

Requirements?

A

Succinyl CoA Succinate (step 5 of TCA, start of OAA regeneration)

Reversible

Requirements: GDP and Pi

**GTP produced

36
Q

Reaction catalyzed by succinate dehydrogenase?

Requirements?

A

Succinate Fumarate (step 6 of TCA)

Reversible; Enzyme is in mitochondrial inner membrane (Complex II of ETC)

Requirement: FAD

**1ST AND ONLY FADH2 PRODUCED

37
Q

Reaction catalyzed by Malate Dehydrogenase?

Requirements?

A

L-Malate Oxaloacetate (step 8 of TCA)

Reversible; not very favorable but it’s ok b/c step 1 of TCA is very favorable

Requirement: NAD+

**3RD AND FINAL NADH GENERATED, REGENERATION OF OAA SO TCA WILL RESTART

38
Q

How much ATP via equivalents is produced via TCA?

A

10-12 ATP (depending on tissue; brain and skeletal m. will produce less b/c they use glycerol phosphate shuffle)

39
Q

PDH deficiency (E1 deficiency specifically)

A

Causes congenital lactic acidosis (because pyruvate gets reduced to lactate instead)
- neurologic symptoms b/c brain is sensitive to lactic acidosis

40
Q

Leigh syndromes (subacute necrotizing encephalomyelopathy)

A
  • Either a PDH deficiency or a PC deficiency (30 possible gene mutations)
    Causes lactic acidemia and respiratory failure
41
Q

Beriberi disease/Wernicke-Korsakoff syndrome (similar mech)

A
  • Thiamine deficiency

cofactor of PDH, Alpha-ketoglutarate dehydrogenase

42
Q

Reaction catalyzed by Pyruvate carboxylase (PC)?
Requirements?
Regulation?

A

Pyruvate –> oxaloacetate

Irreversible

  • Oxidative step in gluconeogenesis to overcome step 10 in glycolysis
  • Also anapleroic reaction for TCA (restore OAA levels)

Requirements: Biotin, ATP (x2), Mg2+, CO2

Takes place in mitochondria

Regulation: allosterically activated by Acetyl CoA

43
Q

Reaction catalyzed by phosphoenolpyruvate carboxykinase?

Requirements?

A

Oxaloacetate –> Phopsphoenol pyruvate

Irreversible
- Oxidative step in gluconeogenesis to overcome step 10 in glycolysis

Requirements: GTP (x 2)
- Note: CO2 is released

1/2 mitochondrial, 1/2 cytosolic in humans

44
Q

Reaction catalyzed by fructose-1,6-bisphasphotase?

Requirements?

A

Fructose 1,6-bisphosphate –> Fructose 6-phosphate

Irreversible
- Oxidative step in gluconeogenesis to overcome step 3 in glycolysis

Requirements: just H2O
Phosphate released

45
Q

Regulation of Fructose-1,6-bisphosphatase?

A

Inhibition: (allosteric) Fructose-2,6-bisphosphate (Insulin/Glucagon), AMP

46
Q

Reaction catalyzed by glucose 6-phosphatase?

Requirements?

A

Glucose 6-phosphate –> Glucose

Irreversible
- Oxidative step in gluconeogenesis to overcome step 1 in glycolysis

Requirement: just H2O
Phosphate released

**LIVER AND KIDNEYS ONLY RELEASE FREE GLUCOSE

47
Q

What are reactions in gluconeogenesis that require ATP?

A

3-phosphoglycerate 1,3-phosphoglycerate (x 2)

Enzyme: Phosphoglycerate kinase

48
Q

What are reactions in gluconeogenesis that require NADH?

A

1,3-phosphoglycerate glyceraldehyde 3-phospate (x2)

Enzyme: glyceraldehyde phosphate dehydrogenase

49
Q

How much energy/reagents does gluconeogenesis require?

A

6 ATP, 2 NADH

50
Q

What are the precursors of gluconeogenesis?

A
  • Lactate (converted to pyruvate by Lactate DeHydrogenase)
  • alpha-keto acids and amino acids (from catabolism of glucogenic AAs, form oxaloacetate)
  • Glycerol (converted to glycerol-3-phosphate by glycerol kinase –> from hydrolysis of triglycerides)
51
Q

What states result in gluconeogenesis regulation?

A
  • Fasting
  • Prolonged exercise
  • High protein diet
  • Stress or injury
  • Substrate availability (lactate, pyruvate, glucogenic AAs, glycerol)
52
Q

What is alcohol’s effect on gluconeogenesis?

A
  • Alcohol metabolism reduces NAD+ to NADH (NAD+ is needed for glycerol-P-dehyrogenase and LDH)
  • Less NAD+ means less gluconeogenesis and more lactate buildup
  • This can result in hypoglycemia and lactic acidosis
53
Q

Which enzymes in the pentose phosphate pathway particpate in reactions that generate NADPH?

A
  • Glucose 6-P dehydrogenase (G-6-P to 6-phosphogluco-delta-lactone)- 1st oxidative reaction
    ^(negative feedback from NADPH!!!)
  • 6-phoshogluconate dehydrogenase (6-phosphogluconate to ribulose 6-phosphate) - 3rd oxidative reaction
54
Q

Glucose 6-P dehydrogenase deficiency mechanism

A
  • Less NADPH–> less (reduced) glutathione–> more reactive oxygen species -> more damaged hemoglobin –> more hemoglobin aggregation –> Heinz bodies –> weak/fragile RBCs –>hemolysis (hemolytic anemia)

NOTE: TOTAL absence is LETHAL, usually decreased activity

55
Q

Reaction catalyzed by Glycogen phosphorylase?

Requirements?

A

Phosphorolysis of glycogen at alpha(1->4) linages using inorganic phosphate donation to oxygen of the glycosidic bond (glycogen breakdown)

One residue at a time
Irreversible, regulated

Requirement: Vitamin B6 (PLP, pyridoxyl phosphate)

56
Q

Reaction catalyzed by debranching enzyme?

A

Two functions (glycogen breakdown):

  • 4:4 glucan transferase: transfer 3 outer glucoses on branch to non-reducing end of chain
  • alpha-1,6- glucosidase removes remaining glucose that is alpha 1,6 linked (releases as FREE GLUCOSE, little)
57
Q

Phosphoglucomutase reacton?

A

Converts glucose 1-P to glucose 6-P

  • At the end of glycogen phosphorylase’s action, where only G-1-P remains
  • Also 1st step of glycogen synthesis
    • reversible reaction
58
Q

Glucose-6-phosphate translocase action?

A

Enzyme that transports G-6-P into Endoplasmic Reticulum on LIVER/kidney cells
- for release to body after broken down to free glucose

Note: in muscle G-6-P is kept in cells for its own use

59
Q

Reaction catalyzed by UDP-glucose phosphorylase?

Requirement?

A

Glucose 1-P –> UDP-glucose +PPi; 2nd reaction in glycogen synthesis

UTP is required

Also PPi breaks down to 2Pi

60
Q

Reaction catalyzed by glycogen synthase?

Requirement?

A

UDP-glucose + Glycogen(n residues) –> Glycogen(n+1 residues) + UDP

One unit at a time

Requirement: Needs a “glycogen primer” of at least 4 residues

61
Q

Reaction catalyzed by glycogenin?

A

Forms primer for glycogen synthesis
- UDP-glucose + tyrosine on glycogenin –> glucose-o-tyrosine benzyl on glycogenin + UDP

Makes 8mer primer, residues added on non-reducing end

62
Q

Reaction catalyzed by (1,4–>1,6)- transferase?

A
  • Branch formation on glycogen

- removes 6-8mer from non-reducing end, attaches it via 1,6 alpha linages, four residues from branch point

63
Q

Glycolysis regulation actions for:

  • Glucose 6 phosphate
  • ATP
  • AMP
  • Glucose
A
  • Glucose 6 phosphate: inhibits glycogen phosphorylase, activates glycogen synthase
  • ATP: inhibits glycogen phosphorylase
  • AMP: activate glycogen phosphorylase (MUSCLE ONLY; Ca2+ also activates glycogen breakdown via nerve stimulation only)
  • Glucose activate glycogen phosphorylase (LIVER ONLY)
64
Q

Important enzymes in fructose metabolism

A
  • Fructokinase: requires ATP, Fructose to Fructose 1-6-P
  • Aldolase B: Fructose 1-6-P to DHAP and Glyceraldehyde
    (Cause of hereditary fructose intolerance)

Eventually gets converted to G3P, used in glycolysis

65
Q

Important enzymes in sorbitol metabolism

A
  • Aldose reductase: Needs NADPH; Glucose to Sorbitol (alcohol of fructose), produced when too much glucose
  • Sorbitol dehydrogenase: Need NAD+, Converts sorbitol to fructose
  • Often sorbitol accumulation is due to hyperglycemia
66
Q

Important enzymes in galactose metabolism

A
  • Galactokinase: ATP needed, Galactose to galactose-6-P
  • Galactokinase deficiency leads to increase galactose in blood and urine, galacticol accumulation, results in cataracts
  • Galactose 1-P Uridyl transferase: Needs UDP galactose (from UDP Glucose via epimerase); converts Galactose 1 P to Glucose 1 P
  • Deficiency results in classic galactosemia, can cause liver damage and other issues

Then converted to glucose 6 P (phosphoglucomutase) for glycolysis/Glucose

67
Q

Glycogen metabolism via Insulin (mechanism)

A

in liver and muscle

  • Stimulates cAMP phosphodiesterase
  • to decrease cAMP levels
  • reducing PKA activity
  • Increases hepatic protein phosphatase activity
  • this inhibits glycogen phosphorylase and its activator, phosphorylase kinase
  • stimulates glycogen synthase (via dephosphorylation) to increase glycogenesis
68
Q

Glycogen metabolism via Glucagon (mechanism)

A

only in liver

  • stimulates G-protein
  • this stimulates adenylyl cyclase
  • increases cAMP
  • increases PKA activity
  • PKA phosphorylates and activates glycogen phosphorylase and phosphorylase kinase (its activator)
69
Q

Glycogen metabolism via Epinephrine (mechanism)

A
  • PKA path in muscle only, both PKA and PLC in liver
  • epi stimulates g-protein
  • G protein stimulates PKA
  • phosphorylation of glycogen phosphorylase and phosphoryl kinase (its activator)
  • epi also stimulates phospholipase C
  • PLC splits PIP2 to IP3 and DAG
  • DAG activates protein kinase C directly, inactivates glycogen synthase (via phosphorylation)
  • IP3 stimulates Ca2+ release to ER, which also activates PKC (which inactivates glycogen synthase)
  • Ca2+ also binds to calmodulin to activate calmodulin dependent kinase and phosphorylase kinase (which activates glycogen phosphorylase)
  • Calmodulin dependent kinase and phosphoryl kinase inactivate glycogen synthase
70
Q

Lipase (FA breakdown)

A
  • TAG to glycerol and fatty acids
  • Regulated by epinephrine and glucagon (because they activate PKA which activates hormone-sensitive lipase in the liver)
  • Insulin activates protein phosphatase 1 which inactivates HSL

*Note: FA are carried in blood via albumin to rest of thebody

71
Q

Thiokinase

A
  • Converts FA to Fatty acyl CoA

- Requires ATP

72
Q

Rate limiting step in fatty acid breakdown?

A

Carnitine shuffle in long chain fatty acid oxidation

  • In intermembrane space of mitochondria:
    Attaches Carnitine to FA CoA via CPT-1 (carnitine palitoyl transferase 1) to facilitate diffusion across inner mitochondiral membrane

**CPT 1 is inhibited by Malonyl CoA (product during synthesis, Malonyl CoA in inhibited by high AMP and PKA)

  • Once in Mit membrane, CPT-2 converts back to fatty acyl coA
73
Q

Fatty Acyl coA synthetase

A
  • ATP + FA to FAcyl AMP + PPi to Fatty Acyl coA

For intracellular activation of Fatty acyl coA

74
Q

Acyl CoA Dehdrygeonases

A

Many Enzymes in reaction, convert Fattyl Acyl CoA to Enoyl CoA

  • B oxidation reaction, FA breakdown
  • Need FAD+, reaction produces FADH2
75
Q

Enoyl CoA hydratase (general action)

A

Hydrolyses double bond in Enoyl CoA

76
Q

3-hydroxyacetyl CoA dehydrogenase (general action)

A

Converts hydrated Enoyl coA (3-hydroxyacyl CoA) to ketone (3-ketoacyl coA)

-Need NAD+, to produce NADH

77
Q

Beta-ketoacyl-CoA (general action)

A
  • Breaks up 3-ketoacyl CoA to a fatty acyl CoA (-2 Cs) and acetyl coA
  • The shorter FA COA is used for next round of beta oxidation (beta oxidation spiral)
  • Need CoA
78
Q

What happens when breaking down odd # C FA chain?

A
  • Last 3 cs released as Propionyl CoA
  • Converted to succinyl coA with three enzymes:
    1. Propionyl CoA carboxylase (requires biotin, ATP, CO2)
    2. Racemase- converts D to L isomer
    3. Mutase- Converts to succinyl coA (needs vitamin B12)
79
Q

HMG CoA Synthase

A
  • EZ in ketone body synthesis
  • Converts Acetoacetyl Co A to 3-hydroxy-3-methyl glutaryl CoA

** RATE LIMITING STEP

80
Q

HMG CoA Lyase

A

Converts 3-hydroxy-3-methyl glutaryl CoA (3HMG CoA)

to AcetoAcetate

81
Q

D-Beta hydroxybutrate dehydrogenase

A
  • AcAc to D-Beta hydroxybutrate (BHB)
    (NEED NADH)
  • AcAc also spontaneously releases acetone
82
Q

Malic Enzyme

A
  • Part of shuttle in FA synthesis to transport Acetyl CoA to cytosol from mitochondria (done by converting to citrate, then malate, then pyruvate)
  • small amount of NADPH produced in step (nothing much)
  • Converts Malate to pyruvate in cytosol

(PDH will then convert it back to Acetyl CoA)

Need NADP+

83
Q

Acetyl CoA carboxylase

A

Converts Acetyl CoA to Malonyl CoA

Malonyl CoA can inhibit CPT-1 in carnitine shuttle in FA breakdown

***RATE LIMITING STEP IN FA SYNTHESIS

Needs Biotin

  • Activated by citrate, insulin
  • Inhibited by Palmitoyl CoA, AMP, Glucagon, Epinephrine
84
Q

Fatty Acid Synthase

A
  • 7 separate enzymes in complex that convert Malonyl CoA to Palmitate to Palmitoyl CoA!
  • Uses CoA for 2 additional Cs at beginning
  • EZ is a vitamin B derivative
  • Panothenic acid is also part of complex (transfers intermediates between sites on EZ complex)
  • Condensation, Decarboxylation, Reduction with NADPH x 2, dehydration reactions occur

**ELONGATIon beyond 16 C occurs in smooth ER, similar mechanism as FA synthase, Malonyl CoA and NADPH needed

85
Q

Where does desaturation of FA occur? What enzyme?

A
  • In ER, can only form chains with CIS double bonds
  • Done by mixed function oxidase (desaturase)
  • Need NADH, O2, Cytochrome b5

For trans double bonds, we need linoleate and linolenate

86
Q

Regulation of FA synthesis

A

A. Fed state: INSULIN↑, Fatty acid synthesis active, malonyl CoA blocks fatty acid transport into mitochondria, preventing FA oxidation

B. Fasted state: GLUCAGON↑ , EPINEPHRINE↑ , INSULIN ↓; this activates Protein Kinase A via cAMP.

  1. Hormone sensitive lipase is active via phosphorylation by protein kinase A
  2. Acetyl CoA carboxylase is inactive (phosphorylated),
    preventing malonyl CoA formation.
  3. Lack of malonyl CoA permits fatty acids transport (CPT-I)
    into mitochondria for oxidation.

Foundations (9 decks)

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