Study Set Content:
Michaelis-Menten
Equation
Michaelis-Menten Curve
is an important characteristic of an enzymecatalyzed reaction and is significant for its biological function.
KM
The physiological consequence of KMis illustrated by the sensitivity of some individuals to
ethanol
• The physiological consequence of KMis illustrated by the sensitivity of some individuals to ethanol. Such persons exhibit facial flushing and rapid heart rate (tachycardia) after ingesting even small amounts of alcohol. In the liver, alcohol dehydrogenase converts ethanol into
acetaldehyde
Normally, the acetaldehyde, which is the cause of the symptoms when present at high concentrations, is processed to acetate by
acetaldehyde dehydrogenase.
Most people have two forms of the acetaldehyde dehydrogenase, a low KM mitochondrial form and a high KM
cytosolic form
Most people have two forms of the acetaldehyde dehydrogenase, a low KM mitochondrial form and a high KM cytosolic form. In susceptible persons, the mitochondrial enzyme is less active due to the substitution of a
single amino acid
glutamate to lysine substitution at position
487
common in (blank) Asian population
50%
Most people have two forms of the acetaldehyde dehydrogenase, a low KM mitochondrial form and a high KM cytosolic form. In susceptible persons, the mitochondrial enzyme is less active due to the substitution of a single amino acid (glutamate to lysine substitution at position 487; common in 50% Asian population), and acetaldehyde is processed only by the
cytosolic enzyme.
Most people have two forms of the acetaldehyde dehydrogenase, a low KM mitochondrial form and a high KM cytosolic form. In susceptible persons, the mitochondrial enzyme is less active due to the substitution of a single amino acid (glutamate to lysine substitution at position 487; common in 50% Asian population), and acetaldehyde is processed only by the cytosolic enzyme. Because this enzyme has a high KM, less acetaldehyde is converted into
acetate
excess acetaldehyde escapes into the blood and accounts for the
physiological effects
To put it simply, the (blank) is the one responsible for the conversion of acetaldehyde to acetate
mitochondrial form
To put it simply, the mitochondrial form is the one responsible for the conversion of acetaldehyde to acetate but because it is less active it cannot perform this function. In the case of cytosolic enzyme, it has a high Km, meaning it does not bind efficiently to the substrate (acetaldehyde) so less acetaldehyde is converted to
acetate
Vmax reveals the (blank) of an enzyme
turnover number
umber of substrate molecules converted into product by an enzyme molecule in a unit time when the enzyme is fully saturated with substrate.
turnover number
Turnover number per second
Carbonic anhydrase
600,000
3-Ketosteroid isomerase
280,000
