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Metabolism > Enzymes > Flashcards

Enzymes Flashcards

1
Q

Glucokinase

A

Step 1- glycolysis (in liver)
Glucose–> G6P
higher Km- lower affinity
Indirectly inhibited by Fructose 6 Phosphate

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2
Q

Phosphofructokinase (PFK)

A

Step 3- glycolysis
Fructose 6 Phosphate–>Fructose-1,6-bis Phosphate
MUSCLE- allosterically inhibited by high ATP
- stimulated by high AMP
LIVER- controlled by insulin:glucagon
- well fed activates (high insulin)
- starvation inhibits glycolysis (high glucagon)

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3
Q

Pyruvate Kinase

A

Step 10- glycolysis
Phosphoenylpyruvate (PEP)–> Pyruvate
activated by high insulin:glucagon

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4
Q

Hexokinase

A

Step 1- glycolysis
catalyses Glucose–>Glucose 6 Phosphate
Allosterically inhibited by G6P
Low Km- high affinity for Glucose

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5
Q

Lactate Dehydrogenase

A

pyruvate–> lactate
is reduction
converts NADH–>NAD+

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6
Q

Sucrose Metabolism (3 enzymes)

A

Sucrase-
sucrose–>fructose + glucose

Fructokinase-
fructose–>fructose-1-Phosphate

Aldolase-
fructose——> 2x Glyceraldehyde-3-Phosphate

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7
Q

Aldolase

A

Fructose1P—–>Glyceraldehyde3P (intermediate of Glycolysis)
if missing- Fructose Intolerance
F1P accumulates in liver—> liver damage

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8
Q

Fructokinase

A

Fructose—>F1P

if missing- essential fructosuria

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9
Q

Lactase

A

lactose–>galactose + glucose

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10
Q

galactokinase

A

Galactose–>Galactose-1-Phosphate
deficiency- rare
galactose accumulates- reduced to galactitol

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11
Q

Aldose Reductase

A

(Think ‘itol’)
Galactose–> Galactitol
Also Glucose–> Sorbitol

reduction
NADPH–>NADP+

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12
Q

(galactose-1-P) Uridyl Transferase

A

Galatose-1-P –> Glucose-1-P
converts UDP-glucose –> UDP Galactose

if deficiency- galactose & galactose-1-P build up
causes tissue damage

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13
Q

UDP-Galactose-4-epimerase

A

UDP-Glucose–>UDP-Galactose

this converts galactose-1-P to glucose-1-P

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14
Q

Glucose-6-Phosphate Dehydrogenase

A 
Pentose Phosphate Pathway
Glucose-6-P --> 5C sugars 
(nucleotides, F6P)
Controlled by NADP+/NADPH ratio
nadp+ activates
nadph inhibits
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15
Q

Glutathione Reductase

A

GSSG–> 2 x GSH (Glutathione)
NADPH–> NADP+
Reduces oxidised glutathione back to its reduced, active form by breaking its disulphide bridges

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16
Q

Glutathione Peroxidase

A

catalyses reaction of two reactive glutathiones to form oxidised GSSH.
Requires Selenium
The e- lost from GSH stabilises a ROS

17
Q

Pyruvate Dehydrogenase

A

converts pyruvate to Acetyl CoA

irreversible reaction

18
Q

Acetyl CoA Carboxylase

A 
converts Acteyl CoA--> Malonyl CoA
uses ATP
Regulation- 
activated- 
Insulin (dephosphorylation) & Citrate (allosteric)

Inhibited-
Glucagon/Adrenaline (phosphorylation) & AMP (allosteric)

19
Q

Fatty Acyl CoA synthase

A

in fatty acid catabolism

facilitates activation of fatty acids by linking a co-enzyme A

20
Q

Kinase enzymes

A

phosphorylate their substrate

eg Glycerol Kinase phosphorylates glycerol

21
Q

Two major enzymes for Gluconeogenesis

A

PEPCK- (phospoenolpyruvate)

Fructose 1,6-bisphosphatase

22
Q

Hormone Sensitive Lipase

A

TAGs–> fatty acids + glycerol

sensitive to insulin levels- high insulin decreases activity

23
Q

Hormone Sensitive Lipase

A

TAGs–> fatty acids + glycerol

sensitive to insulin levels- high insulin decreases activity

24
Q

Kinase enzymes

A

phosphorylate their substrate

eg Glycerol Kinase phosphorylates glycerol

25
Q

Thyroid Peroxidase

A

Facilitates the incorporation of iodine to thyroglobulin

Membrane bound enzyme

26
Q

What do kinase enzymes do?

A

Add a Phosphate group

Eg hexokinase

27
Q

What does cystathionine B-synthase catalyse?

A

Homocysteine–> cystathionine

28
Q

What condition if it where there is a deficiency in cystathionine B-synthase?

A

Homocystinuria

29
Q

What co-factor is needed for the enzyme deficient in Homocystinuria?

A

Cystathionine B-synthase

Active vitamin B6

30
Q

What enzyme is defective in PKU?

A

Phenylalanine hydroxylase

31
Q

What does phenylalanine hydroxylase catalyse?

A

Phenylalanine–> tyrosine

32
Q

Lysyl Oxidase

A

Collagen synthesis

Catalyses formation of covalent cross links between collagen FIBRILS to form collagen FIBRES

33
Q

Prolyl Hydroxylase

A

Collagen synthesis

Catalyses hydroxylation of selected …..residues

34
Q

Procollagen peptidase

A

Collagen synthesis

Catalyses removal of N&C terminal propeptides

35
Q

Alkaline Phosphatase

A

Clinical marker of bone turnover

Enzyme present on osteoblasts

Metabolism (10 decks)

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