Recitation #5: Enzyme Kinetics
Given Information:
vo = Vmax[S]/(KM+[S]) KI = [E][I]/[EI] K′I = [ES][I]/[ESI]
vo = Vmax[S]/( KM+’[S]) = 1 + ([I]/KI) ′ = 1 + ([I]/K′I)
k = (kBT/h)e-(ΔG‡/RT) TK = TC + 273
kB = 1.3806488 × 10-23 m2 kg s-2 K-1 h = 6.62606957 × 10-34 m2 kg / s
R = 0.008314 kJ mol K -1 -1 Std. Temp = 298 K
Case Study:
A father rushes a child to the hospital emergency room after the child accidentally drank
antifreeze. The attending physician immediately orders a gastric lavage (stomach pump)
and alcohol dehydrogenase (ADH) inhibitor. The doctor then questions the father and
child about how long ago the child drank the antifreeze, the amount ingested, and the
type of antifreeze. The father replies, “maybe a ¼ cup 25 minutes ago” and then calls a
neighbor to send photos of the antifreeze bottle in the garage.
The ER staff places an intravenous catheter in the girl’s arm and administers a dose of an
alcohol dehydrogenase (ADH) inhibitor called fomepizole. Just as the girl is about to
have her stomach pumped, a text arrives with a photo of the original antifreeze container.
The ER doctor closely examines the picture and then turns to the girl's father, "You're
sure this is what she drank?"
“Yes—just what's missing from the bottle."
The doctor smiles as he turns towards the little girl, "Young miss, you're going to be just
fine." To the nurse and father, "We'll cancel the lavage and she won’t need kidney
dialysis. With the ADH inhibitor she's already on, we just need to give her more IV fluids
and have her drink water to flush out her system. We’ll monitor her for another couple of
hours, but then you can both go home." The father, simultaneously relieved and confused,
exclaims, "What? But, how is it that this was so serious a minute ago and now we can
just leave?” The doctor replies,“Most antifreezes use ethylene glycol, while this
antifreeze uses propylene glycol. Everything is toxic in high enough doses, but ethylene
glycol is much more toxic than propylene glycol.”
, Ingested alcohols are absorbed by the digestive tract and circulated to the liver where
they are metabolized. The liver has enzymes that will oxidize a wide variety of potential
toxins, so that they become more polar and can be easily eliminated in urine. In the case
of alcohols, the liver uses alcohol dehydrogenase (ADH) to convert the hydroxyl to a
carbonyl group and aldehyde dehydrogenase (ALDH) to convert aldehydes to carboxylic
acids as shown below:
Note R and/or R′ may be a hydrogen.
Both ADH and ALDH are considered promiscuous enzymes as they can convert a few
different substrates to products. The KM values for ADH with some common alcohols
are shown below:
Alcohol KM (M)
Ethanol 0.021
Methanol 0.13
Isopropanol 0.14
(rubbing alcohol)
Source: Sigma-Aldrich datasheet at https://www.sigmaaldrich.com/content/dam/sigma-
aldrich/docs/Sigma/Datasheet/6/a7011dat.pdf
Case Study adapted from Toxic Alcohols: A Case Study on Enzyme Function (by Justin
Hines, Lafayette College. Berg 9th ed.)
Given Information:
vo = Vmax[S]/(KM+[S]) KI = [E][I]/[EI] K′I = [ES][I]/[ESI]
vo = Vmax[S]/( KM+’[S]) = 1 + ([I]/KI) ′ = 1 + ([I]/K′I)
k = (kBT/h)e-(ΔG‡/RT) TK = TC + 273
kB = 1.3806488 × 10-23 m2 kg s-2 K-1 h = 6.62606957 × 10-34 m2 kg / s
R = 0.008314 kJ mol K -1 -1 Std. Temp = 298 K
Case Study:
A father rushes a child to the hospital emergency room after the child accidentally drank
antifreeze. The attending physician immediately orders a gastric lavage (stomach pump)
and alcohol dehydrogenase (ADH) inhibitor. The doctor then questions the father and
child about how long ago the child drank the antifreeze, the amount ingested, and the
type of antifreeze. The father replies, “maybe a ¼ cup 25 minutes ago” and then calls a
neighbor to send photos of the antifreeze bottle in the garage.
The ER staff places an intravenous catheter in the girl’s arm and administers a dose of an
alcohol dehydrogenase (ADH) inhibitor called fomepizole. Just as the girl is about to
have her stomach pumped, a text arrives with a photo of the original antifreeze container.
The ER doctor closely examines the picture and then turns to the girl's father, "You're
sure this is what she drank?"
“Yes—just what's missing from the bottle."
The doctor smiles as he turns towards the little girl, "Young miss, you're going to be just
fine." To the nurse and father, "We'll cancel the lavage and she won’t need kidney
dialysis. With the ADH inhibitor she's already on, we just need to give her more IV fluids
and have her drink water to flush out her system. We’ll monitor her for another couple of
hours, but then you can both go home." The father, simultaneously relieved and confused,
exclaims, "What? But, how is it that this was so serious a minute ago and now we can
just leave?” The doctor replies,“Most antifreezes use ethylene glycol, while this
antifreeze uses propylene glycol. Everything is toxic in high enough doses, but ethylene
glycol is much more toxic than propylene glycol.”
, Ingested alcohols are absorbed by the digestive tract and circulated to the liver where
they are metabolized. The liver has enzymes that will oxidize a wide variety of potential
toxins, so that they become more polar and can be easily eliminated in urine. In the case
of alcohols, the liver uses alcohol dehydrogenase (ADH) to convert the hydroxyl to a
carbonyl group and aldehyde dehydrogenase (ALDH) to convert aldehydes to carboxylic
acids as shown below:
Note R and/or R′ may be a hydrogen.
Both ADH and ALDH are considered promiscuous enzymes as they can convert a few
different substrates to products. The KM values for ADH with some common alcohols
are shown below:
Alcohol KM (M)
Ethanol 0.021
Methanol 0.13
Isopropanol 0.14
(rubbing alcohol)
Source: Sigma-Aldrich datasheet at https://www.sigmaaldrich.com/content/dam/sigma-
aldrich/docs/Sigma/Datasheet/6/a7011dat.pdf
Case Study adapted from Toxic Alcohols: A Case Study on Enzyme Function (by Justin
Hines, Lafayette College. Berg 9th ed.)
