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Enzymes Involved in Metabolism Flashcards

1
Q

glucokinase

  1. Used for…
  2. Relationship to metabolism…
A
  1. phosphorylates glucose to glucose-6-phosphate (and is not subject to product inhibition)
  2. LIVER ENZYME ONLY (?)
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2
Q

Hormone Sensitive Lipase (HSL)

  1. Used for…
  2. Relationship to metabolism…
A
  1. degrades triglycerides in adipose tissue

2. Insulin inhibits HSL by promoting its dephosphorylation (inactivation). Thus, insulin decreases TG breakdown.

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3
Q

Glycerol-3-Phosphate

  1. Used for…
  2. Relationship to metabolism…
A
  1. Backbone of for trigylceride synthesis

2. Glucose mobilization into Adipocytes via insulin provides Glycerol-3-Phosphate as a substrate for TG synthesis

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4
Q

Lipoprotein Lipase (LPL)

  1. Used for…
  2. Relationship to metabolism…
A
  1. Allows for drop off (release) of fatty acids from chylomicrons, which are subsequently for TG synthesis and storage in adipocytes
  2. insulin increases synthesis of Lipoprotein Lipase
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5
Q

Insulin sensitive glucose transporters

A

GLUT 4 (in skeletal & cardiac muscle and adipocytes)

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6
Q

Pyruvate Kinase

  1. Used for…
  2. Relationship to metabolism…
A

1.

2.

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7
Q

Acetyl CoA Carboxylase

  1. Used for…
  2. Relationship to metabolism…
A
  1. Catalyzes reaction of Acetyl Coa –> Malonyl CoA (rate-limiting run for FA synthesis!)
  2. in fed state, insulin levels result in an increased synthesis of this enzyme. Malonyl CoA subsequently inhibits fatty acid oxidation.
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8
Q

Fatty Acid Synthase

  1. Used for…
  2. Relationship to metabolism…
A

1.

2.

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9
Q

Adenylyl Cyclase

  1. Used for…
  2. Relationship to metabolism…
A
  1. Causes signaling cascade leading to phosphorylation
  2. Activated by glucagon binding at the plasma membrane –> activates cAMP-dependent protein Kinase –> phosphorylation of enzymes (resulting in activation or inactivation)
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10
Q

Alcohol dehydrogenase

  1. Used for…
  2. Relationship to metabolism…
A
  1. Converts ethanol to acetaldehyde by reducing NAD+ to NADH
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11
Q

Aldehyde Dehydrogenase

  1. Used for…
  2. Relationship to metabolism…
A
  1. converts Acetaldehyde to Acetate by reducing NAD+ to NADH
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12
Q

fructose-2,6-bisphosphate

  1. Used for…
  2. Relationship to metabolism…
A
  1. Allosteric activator of phosphofructokinase-1 (PFK1) and allosteric inhibitor of fructose-1,6-bisphosphatase
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13
Q

Phosphofructokinase-1 (PFK1)

  1. Used for…
  2. Relationship to metabolism…
A
  1. glycolysis
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14
Q

Fructose-1,6-bisphosphatase

  1. Used for…
  2. Relationship to metabolism…
A
  1. gluconeogenesis
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15
Q

Fructose-1,6-bisphosphatase

  1. Used for…
  2. Relationship to metabolism…
A
  1. gluconeogenesis
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16
Q

HMG-CoA Reductase

A
  1. involved in anabolic metabolism

2. in fed state, insulin levels result in an increased synthesis of this enzyme

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17
Q

HMG-CoA Reductase

  1. Used for…
  2. Relationship to metabolism…
A
  1. involved in anabolic metabolism

2. in fed state, insulin levels result in an increased synthesis of this enzyme

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18
Q

Glycogen Synthase

  1. Used for…
  2. Relationship to metabolism…
A
  1. conversion of glucose-6-phosphate to glycogen

2. activated by dephosphorylation AND by increased availability of glucose-6-phosphate (allosteric effector)

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19
Q

NADPH used in what kind of reactions

A

synthesis reactions ?

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20
Q

NADH and NADPH are

A

reducing equivalents?

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21
Q

NAD+ used in what kind of reactions

A

oxidation reactions ?

22
Q

HMP Pathway (Hexose monophosphate)

A

Produces NADPH, which is required for fat synthesis

23
Q

Acetyl CoA

A

used as a building block for fatty acid synthesis
OR
provides energy by oxidation in the TCA cycle

ALSO- allosteric activator of pyruvate carboxylase which pushes towards gluconeogenesis. It is an allosteric inhibitor of pyruvate dehydrogenase (pyruvate–>lactose?)

24
Q

Pyruvate Carboxylase

  1. Used for…
  2. Relationship to metabolism…
A
  1. Catalyzes first step in gluconeogenesis
  2. Inactive when there are low levels of Acetyl CoA –> meaning that the acetyl CoA is being used for fatty acid synthesis
25
Fatty acid synthesis favored by...
Availability of substrates: Acetyl CoA and NADPH & Activation of Acetyl CoA Carboxylase: by dephosphorylation and presence of allosteric activator Citrate
26
Hexokinase 1. Used for... 2. Relationship to metabolism...
1. phosphorylates glucose to glucose-6-phosphate in SKELETAL MUSCLE 2. increase in glucose-6-phosphate favors glycogen synthesis, especially if glycogen stores have been depleted as a result of exercise
27
Transaminase 1. Used for... 2. Relationship to metabolism...
1. degradation of branched-chain amino acids (leucine, isoleucine, valine) in MUSCLE ONLY 2. branched-chain amino acids escape metabolism by the liver are are subsequently used in muscle for protein synthesis and as a source of energy
28
Glucose-6-phosphatase 1. Used for... 2. Relationship to metabolism...
1. | 2. Allows production of free glucose from both glycogenolysis and gluconeogenesis
29
Where are the carbon skeletons for gluconeogenesis derived?
glucogenic amino acids & lactate from muscle. | glycerol from adipose.
30
Ketogenesis is favored when...
The concentration of Acetyl CoA (from FA B-oxidation) exceeds the oxidative capacity of the TCA Cycle
31
After 3 weeks of fasting, muscle...
muscle decreases its use of ketone bodies from the liver as fuel. It oxidizes fatty acids almost exclusively. This then leads to a further increase in the already elevated levels of ketone bodies.
32
After 3 weeks of fasting, muscle...
muscle decreases its use of ketone bodies from the liver as fuel. It oxidizes fatty acids almost exclusively. This then leads to a further increase in the already elevated levels of ketone bodies.
33
Important glucogenic amino acids released from muscle...
Alanine and glutamine... which are produced by the catabolism of branched-chain amino acids
34
glutamine is released from muscle's metabolism of branched-chain amino acids and is taken up by the kidney, and......
is converted to a-ketoglutarate (+ ammonia, NH3) by renal glutaminase and glutamate dehydrogenase. a-ketoglutarate can be used as a substrate for gluconeogenesis. NH3 picks up H+ from keto body dissociation and is excreted in urine as NH4+ (ammonium). This would cause a shift in increased urine ammonium and decreased urine urea.
35
essential fatty acids
omega-6 fatty acids (precursor of arachidonic acid) and omega-3s????
36
lactate dehydrogenase
pyruvate --> lactate when NADH/NAD+ ratio is high, reaction is virtually irreversible, favoring lactose formation and DEPLETING the *gluconeogenic* substrate, PYRUVATE (alcohol!!!)
37
pyruvate dehydrogenase
pyruvate --> acetyl CoA
38
High NADH/NAD+ ratio favors...
pyruvate --> lactate oxaloacetate --> malate (by malate dehydrogenase) *High NADH/NAD+ suppresses gluconeogenesis
39
Tissues unaffected by insulin levels
brain and RBCs and liver (dbl check?)
40
insulin effect on HSL
inhibits --> decreases lipolysis
41
insulin effect on LPL
stimulates --> which provides fatty acids for synthesis of TGs
42
Skeletal muscle lacks what receptors?
glucagon (it mainly acts on the liver)
43
Metabolic effects of glucagon on carbs, fat, & protein
- CARB: Increases blood glucose by stimulating glycogen breakdown and gluconeogenesis, and by inhibiting glycogen synthesis. - FAT: Inhibits FA synthesis, and stimulates FA oxidation and ketone bodies production. -PROTEIN: Stimulates amino acid uptake and oxidation thus providing the carbon skeleton of amino acids for gluconeogenesis.
44
mechanism of action of glucagon
Glucagon exerts its effects by activating PKA. PKA phosphorylates specific enzymes which results in their activation or inhibition (depending on enzyme).
45
Metabolic effects of catecholamines (epic and norepi)
-Effects very rapid and antagonistic to insulin. -Stimulate lipolysis in adipose tissue. -Stimulate gluconeogenesis and glycogen breakdown in the liver. -Stimulate glycolysis, glycogen breakdown and fatty acid oxidation in skeletal muscle. -The effects of catecholamines are mediated by elevation of cellular cAMP and/or Ca2+ levels.
46
KEY Junctions in metabolism
A. Glucose-6-phosphate | B. Pyruvate and acetyl CoA
47
Phosphoenolpyruvate Carboxykinase (PEPCK) 1. Used for... 2. Relationship to metabolism...
Gluconeogenic enzyme Inhibited by insulin signaling
48
Protein Kinase A 1. Used for... 2. Relationship to metabolism...
Activated by an increase in cAMP in cells. In hepatocytes, cAMP levels increase primarily in response to glucagon and epinephrine.
49
AMPK (AMP Kinase)
AMPK is activated when AMP levels are high. AMP levels accumulate when there have been many ATP-requiring reactions occurring.
50
Metformin
Activates AMPK. AMPK inhibits gluconeogenesis (by inhibiting PEPCK and G6P-ase) and lipogenesis, while promoting fatty acid oxidation and glycolysis.

Gastrointestinal & Nutrition (9 decks)

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