37. Enzyme kinetics**

Question 1

what are enzyme kinetics?

Answer 1

• don’t change equilibrium of rxn
• do not effect free energy change
• change reaciton rate

Question 2

what is reaciton rate?

Answer 2

S <–> P
:d[P]/dt = v = k[S]

• change in P with time
• velocity
• rate constant
• concentration of S

Question 3

what is michaelis-menten kinetics?

Answer 3

• experimentally expressed relationship between rate of formation of product to concentrations of enzyme and substrate
• Vo = (Vmax)([S]) / (Km +[S])
  – initial velocity
  – maximum reaction rate
  – substrate concentration
  – michaelis constant
• Km = [S]
  – when V0 = 1/2 of Vmax

Question 4

what is enzyme saturation (low)?

Answer 4

• low concentration of substrate
  – steap increase in rate of rxn with increasing substrate concentration
• catalytic site of enzyme empty
  – waiting for substrate bind
• rate of which product formed limited by concentration of available substrate

Question 5

what is enzyme saturation (high)?

Answer 5

• as concentration fo substrate increases
  – enzyme becomes saturated with substrate
• as catalytic site is empty
  – more substrate available to bind and react
• rate of formation of product now depends on activity of enzyme

Question 6

how does Km affects enzyme saturation?

Answer 6

• enzyme with high Km
  – low affinity for substrate
  – required greated [S] to achieve Vmax
• rate of rxn when enzyme is satures with substrate is max rate of rxn (Vmax)
• relationship between rate of rxn and [S] depents on affinity of enzyme substrate
  – Km of enzyme

Question 7

what is the assay principle?

Answer 7

• a spec assay works by following a rxn as it progresses from substrates to products
• there must be a shift in the absorbance spectrum of biochemicals present that indicates a change has take place
• setting spec to monitor a certain wavelength range
  – track progess of rxn by disappearance of substrate
  – or appearance of products
• monitoring in real time
  – kinetic assay
• end point assay
  – run rxn for pre determined length of time
  – then treat sample before returning to spec experiment

Question 8

what is G6PDH?

Answer 8

• glucose-6-phosphate (G6P) and oxidised nicotinamide adenin dinucleotide phosphate (NADP+)
  – react ot form 6-phosphogluconolactone (6PGL)
  – and reduced NADPH

Question 9

what are assay components?**

Answer 9

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Question 10

what is the lineweaver-burk plot?

Answer 10

1/v = Km / Vmax[S] + 1 / Vmax