Lecture 10 Flashcards
What enzyme catalyzes the transfer of a C-, N-, or P- containing groups
Transferases
What enzyme catalyzes the cleavage of bonds by addition to water
Hydrolases
What enzyme catalyzes the cleavage of a C-C, C-S, and certain C-N (without water)
Lyases
What enzyme catalyzes racemization of optical/ geometric isomers?
Isomerases
What enzyme catalyzes the formation of bonds between carbon and an N,O,S,C coupled to hydrolysis of high-energy phosphates
Ligase
_______ is a small molecule required for the
catalytic activity of an enzyme.
Cofactor
________ (inorganic) include Cu2+, Fe3+ or Zn2+
Metal ions
When the cofactor is an organic molecule, then
it is a ________. E.g.: vitamins
Coenzyme
When the coenzyme is only transiently
associated, then it is a_________
cosubstrate
When the coenzyme is permanently associated with the protein, either through covalent or non-covalent interactions, then it is a __________
Prosthetic group
_________ is the catalytically active enzyme-cofactor complex.
Holoenzyme
________ is the inactive protein lacking the cofactor.
Apoenzyme
_________ is a small molecule that binds to a larger one
Ligand
_________ is the molecule undergoing the reaction. It is the specific molecule(s) that is bound by the enzyme at its active site.
Substrate
___________ is the region of the enzyme that binds the substrate(s) and where the ________ takes place.
Active site, catalytic reaction
In our cells, groups of enzymes work
together in specific metabolic pathways
consisting of several steps. They are called
___________
Multi-enzyme pathways.
Multi-enzyme pathways can be _______ or
_____________, and they are all __________.
Since some metabolites are shared among
pathways, the fate of a certain metabolite
affects the other pathways.
Linear, branched, interconnected
The slowest step in the pathway
is the _____________.
Rate-limiting step
______________ catalyze the slowest, irreversible step
Rate-limiting enzymes
Rate-limiting steps are targets of _________
and targets of ________ by drugs
Regulation, intervention
Organelles preventing a _______ in enzyme pathways with common products, separating by space
Futile cycle
Seperation in time: Glucose breakdown (glycolysis)
and synthesis (gluconeogenesis) share
enzymes in the same compartment,
but have different ________
Rate-limiting steps
The concentration of many regulatory enzymes
is controlled by ______ and _____
Inducers and inhibitors
Enzyme synthesis is a
Very slow process
Compartmentalization is an important but ________ of regulation
Passive means
Product inhibition; Products display ______ to the
substrate, and cannot be competed off by the
substrate.
Structural similarity
Product inhibition- Products can bind _______ to the active site. The response of the enzyme is _______.
Reversibly, immediate
Facts about allosteric regulators
They have quaternary structure, effector binds at a regulatory site (not active site), they bind reversibly, no need for structural similarity, show sigmoidal curve
Allosteric regulation of enzymes: Classification is based on
Chemical nature of the effector
Allosteric regulation of enzymes;
__________ = true substrate.
__________ = different chemical nature from true substrate.
Homotropic, heterotropic
Allosteric activators (positive effectors) have what effect on enzyme activity, enzyme state, enzyme activity curve
Increase activity, stabilize R-state, shift left
Allosteric inhibitors (negative effectors) have what effect on enzyme activity, enzyme state, enzyme activity curve
Decrease activity, stabilize T-state, shift right
_______________: upstream substrate of a multi-enzyme pathway activates a downstream enzyme.
Feedforward activation
Disease of the day: Pulmonary emphysema may be produced by ______________. As A1A is defective, that leads to increased __________ activity.
alpha1-antitrypsin deficiency (A1AD), neutrophil elastase
What are major risk factors for a1-Antitrypsin deficiency, and where does it effect
Smoking, lungs and liver
Covalent regulation refers to the ________ of specific chemical groups via _______ bonding. They have an ________ effect, either reversible or irreversible. They may _________ enzymatic activity, depending on the enzyme considered.
Addition or removal, covalent, immediate, increase or decrease
Many enzymes are produced in an inactive precursor form called ________
Proenzyme or zymogen
Proteolytic cleavage results in an _________ conformational change that exposes the active site
Irreversible
