Enzyme regulation

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36 Terms

1

What molecules can decrease hexokinase activity?

Glucose-6-phosphate, acts as a non-competitive inhibitor

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2

How does the conformation of hexokinase change for catalysis?

Binding of glucose leads to a conformational change, traps glucose into the enzyme ensuring a reaction with ATP

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3

How is glucokinase controlled?

Not inhibited by glucose-6-phosphate, only acts in high glucose concentrations due to low affinity

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4

How can pyruvate kinase activity be increased by allosteric control?

Fructose-1, 6-bisphosphate increases activity

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5

How can pyruvate kinase activity be decreased by allosteric control?

ATP and alanine decrease activity.
Phosphorylation of PK is less active

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6

How does fructose-1, 6-bisphosphate increase pyruvate kinase activity?

Increases binding affinity for phosphoenolpyruvate.
Stabilises tetramer formation

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7

How can phosphofructokinase 1 activity be increased?

By fructose-2, 6-bisphosphate and AMP

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8

How can phosphofructokinase 1 activity be decreased?

BY ATP and citrate

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9

How do ATP and AMP affect phosphofructokinase 1 activity?

ATP reduces affinity for fructose-6-phosphate.
AMP reverses ATP inhibitory effect

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10

How are the subunits of phosphofructokinase 2 regulated?

Phosphofructokinase and fructose bisphosphatase 2 activity.
Phosphorylation increases FBPase activity.
Phosphorylation due to PKA

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11

How is the PDC regulated allosterically?

Due to phosphorylation by PDC kinase or dephosphorylation by PDC phosphatase.
Phosphorylated form is less active

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12

What molecules increase PDC phosphatase activity?

Mg2+ and Ca2+

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13

What molecules decrease PDC phosphatase activity?

NADH

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14

What molecules increase PDC kinase activity?

Mg2+, Acetyl-CoA, NADH

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15

What molecules decrease PDC kinase activity?

CoA, pyruvate, ADP

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16

What molecules can decrease citrate synthase activity?

ATP, succinyl CoA.
Succinyl CoA acts as a competitive inhibitor

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17

What molecules increase isocitrate dehydrogenase activity?

ADP

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18

What molecules decrease isocitrate dehydrogenase activity?

ATP, NADH

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19

What molecules decrease α-ketoglutarate activity?

ATP, succinyl CoA, NADH

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20

What increases the action of phosphorylase in muscles?

Adrenaline, electrical stimulation, ATP/AMP levels

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21

What decreases the action of phosphorylase in muscles?

Glucose-6-phosphate

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22

What increases the action of phosphorylase kinase?

PKA, leads to phosphorylation of the β subunit.
Ca2+ binding to δ subunit

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23

What increases the action of fructose-1, 6-bisphosphatase?

Citrate

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24

What decreases the action of fructose-1, 6-bisphosphatase?

Fructose-2, 6-bisphosphate, AMP

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25

What increases the activity of pyruvate carboxylase?

Acetyl CoA

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26

What decreases the activity of phosphoenolpyruvate carboxykinase and pyruvate carboxylase?

ADP

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27

How does insulin regulate glycolytic enzymes?

Promotes expression of phosphofructokinase 1, pyruvate kinase, phosphofructokinase 2

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28

How does glucagon regulate gluconeogenic enzymes?

Increases expression of phosphoenolpyruvate carboxykinase, and fructose-1, 6-bisphosphatase

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29

How can fatty acid synthesis and oxidation be reciprocally regulated?

Malonyl CoA (synthesis) and palmitoyl CoA (oxidation) inhibit each others synthesis

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30

How is β-oxidation regulated rapidly?

Regulated by substrate availability and the rate of lipolysis
Malonyl CoA inhibits carnitine palmitoyltransferase so inhibits LCFA uptake for β-oxidation

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31

How can β-oxidation be regulated in the long term?

Transcriptional control due to peroxisome proliferator activated receptor (PPARα). Upregulates genes involved in β-oxidation

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32

How can acetyl CoA carboxylase be regulated?

Polymerisation due to citrate or depolymerisation due to palmitoyl CoA.
Phosphorylation due to ATP/AMP or glucagon (phosphorylation)/insulin (dephosporylation)

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33

How can acetyl CoA carboxylase be phosphorylated?

Phosphorylated by AMPK, activated by high AMP and low ATP. Causes formation of inactive ACCb form

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34

How can dephosphorylation regulate acetyl CoA carboxylase?

De-phosphorylated by protein phosphatase 2, causes formation of active ACCa.
Dephosphorylation causes activation of fatty acid synthesis

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35

How can cholesterol synthesis be reguilated?

By regulation of HMG CoA reductase

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36

How is bile acid synthesis regulated?

Regulate their own synthesis via nuclear receptors, bind to FXR, LXR, or LRH-1

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