ENZYMES Flashcards
(requires ATP)
synthetase
(no ATP required)
synthase
(uses water to remove phosphoryl group)
phosphatase
(uses Pi to break a bond and generate a phosphorylated product)
phosphorylase
catalyzes removal of H+ ions
dehydogenase
(O2 is the acceptor, and oxygen atoms are not incorporated into substrate)
oxidase
(one or both oxygen atoms are incorporated)
oxygenase
is a complete enzyme that consists of an apoenzyme and a cofactor.
Holoenzyme
is the protein part of the enzyme
is the protein part of an enzyme that is inactive without its cofactor.
apoenzyme
is the non-protein part.
is essential for the enzyme to function.
cofactor
is a type of cofactor that is an organic molecule.
typically tightly bound to the apoenzyme, but they can be released from the apoenzyme after the reaction is complete
Coenzyme
proposed a simple model that accounts for most of the features of enzyme-catalyzed reactions.
Leonor Michaelis and Maude Menten
In this model, the enzyme reversibly combines with its substrate to form an ES complex that subsequently yields a product, regenerating the free enzyme.
Reaction model
describes the relationship between the rate of an enzyme-catalyzed reaction and the concentration of the substrate.
Michaelis-Menten equation
is characteristic of an enzyme and its particular substrate and reflects the affinity of the enzyme for that substrate.
Km, the Michaelis constant
are regulated by molecules called effectors that bind noncovalently at a site other than the active site.
Allosteric enzymes
effectors that inhibit enzyme activity
Negative effectors
increase enzyme activity
Positive effectors
is when the substrate itself serves as an effector.
They bind to the allosteric site of the enzyme and change its shape, which can either activate or inhibit the enzyme.
Homotropic effectors:
not the same chemical identity as the enzyme’s substrate.
Heterotropic effectors:
is the process of increasing the synthesis of an enzyme. This is usually done in response to a signal molecule, such as a hormone or a nutrient
Induction
is the process of decreasing the synthesis of an enzyme. This is usually done when the cell does not need the enzyme.
Repression
is abundant in the liver.
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