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Biochemistry 2065 > Enzyme Activity Regulation > Flashcards

Enzyme Activity Regulation Flashcards

1
Q

enzyme regulation is important to what 3 reasons

A
  1. avoid problems of substrate cycles
  2. to link energy production and energy usage
  3. to respond to physiological changes
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2
Q

an effective way of regulating complex metabolic pathways is to regulate __ activity

A

enzyme

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3
Q

what are the 6 ways of regulating enzyme activity>

A
  1. substrate level
  2. allosteric/feedback control
  3. covalent modification (on/off switch)
  4. proteolytic cleavgae
  5. isoenzymes
  6. genetic control (transcription regulation)
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4
Q

what is the premise of substrate level control?

A

enzyme activity depends of surrounding concentrations or reactants or products

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5
Q

what is the premise of allosteric control /feedback control?

A

a product will bind reversibly to the first enzyme at its allosteric site (NOT BINDING SITE) and either in inhibit or stimulate production of more

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6
Q

an allosteric effect occurs when a ligand binds to an enzyme and changes what 2 things?

A

shape (conformational change) and therefore activity

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7
Q

allosteric enzymes do not conform to the M-M kinetics because they have a ____ shape caused by ___

A

sigmoidal; homoallostery

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8
Q

what is homoallostery?

A

cooperative substrate binding; binding of one favours the binding of more

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9
Q

allosteric enzymes can take what two forms?

A

tense and relaxed

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10
Q

which form of allosteric enzymes is capable of catalyzing reactions?

A

relaxed

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11
Q

homoallostery abides by what rule?

A

symmetry rule

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12
Q

what is the symmetry rule?

A

must have either all relaxed or all tense

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13
Q

in the absence of substrate or effector, which form or allosteric enzyme is more stable and more present?

A

T

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14
Q

T/F T can sometimes spontaneously turn into r

A

t

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15
Q

what can cause an increase in R-S binding?

A

a positive effector can bind to R to make it more stable and therefore present in higher amounts and more chance to bind to substrate

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16
Q

what can decrease R-S binding

A

a negative effector binding to T and stabilizing it

17
Q

what may result from a loss of allosteric control?

A

pathologic conditions (disease)

18
Q

give an example of a disease caused by lack of allosteric control

A

gout ( build up of urate)

19
Q

what is the premise of covalent modification?

A

a molecule can covalently attach to an enzyme and act as an “on-off” switch

20
Q

what are the two types of covalent modification?

A
  1. covalent activation

2. covalent inhibition

21
Q

describe covalent activation

A

an enzyme in made in its active form and can be turn on

22
Q

describe covalent inhibition

A

an enzyme is made in its inactive form and can be turned off

23
Q

what is the most common type of covalent modification?

A

reversible phosphorylation

24
Q

reversible phosphorylation is catalyses by 2 enzymes

A
  1. protein kinase

2. protein phosphatase

25
Q

what are protein kinases and their role?

A

ATP-dependent enzymes that add a phosphoryl group to a OH group on some enzymes

26
Q

what is the role of protein phosphatase?

A

hydrolyzes side-chain phosphate esters, releasing a phosphoryl group

27
Q

what is the premise of proteolytic cleavage?

A

cutting out a part of an inactive enzyme to make it active

28
Q

what is an inactive precursor enzyme called?

A

zymogen

29
Q

what is the function of a zymogen?

A

inactive because being active in the wrong place/time could be harmful to the cell

30
Q

what is proteolysis?

A

breaking proteins into smaller peptides or amino acids

31
Q

what are isozymes?

A

enzymes that catalyses the same reactions, but have different amino acid sequence

32
Q

what is the premise of isozymes as regulatory control?

A

can be activated by different things, at different stages, allowing for more precise “fine-tuning” of metabolism

33
Q

what is the premise of genetic control in enzyme regulation?

A

induces the expression of an enzyme

Biochemistry 2065 (19 decks)

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