Enzyme Elimination
What is the primary source of the energy enzymes use to reduce activation energies?
noncovalent enzyme-substrate interaction.
What is the steady state?
: the reaction period where [ES] is constant
ATCase catalyzes the conversion of carbamoyl phosphate and aspartate into N-carbamoylaspartate, a precursor in pyrimidine biosynthesis. What roles do ATP and CTP play in this reaction?
heterotropic modulators
A reaction where the rate depends only on the concentration of S is called a _____ reaction.
first order
What are the four kinds of B. Reversible- noncovalent association?
Competitive, Uncompetitive, mixed , non-competitive inhibition
Which type of enzyme inhibitor repeatedly exchanges with the substrate for the active site?
Competitive
What does the y intercept on a Lineweaver-Burk plot represent?
1/Vmax
Penicillin inhibits _____ during peptidoglycan synthesis.
the transpeptidase reaction
Plots of V0 versus [S] for allosteric enzymes produce _____ saturation curves.
sigmoid
What are the three catalytic triad amino acids?
Ser, His, Asp
How is a protein's phosphorylation status regulated?
Different enzymes phosphorylate and dephosphorylate the protein such that activation and deactivation are separately regulated.
Consider the reaction E + S ⇌ ES ⇌ EP ⇌ E + P What do ES and EP represent in the reaction?
reaction intermediates consisting of transient complexes of the enzyme with the substrate and with the product, respectively
What is a cofactor?
an inorganic ion required for enzyme activity
At a substrate concentration that is much greater than the Km for the reaction, which statement is true (assuming the enzyme obeys Michaelis-Menten kinetics)?
The reaction velocity is equal to Vmax.
What are the 4 ways to regulate activity?
Allosteric, Reversible covalent modification, Removal of peptide bonds (proteolytic cleavage), binding of separate (regulatory proteins)
Which type of enzyme inhibitor competes with the substrate for the active site and participates in the initial steps of the reaction before permanently inhibiting the process?
:) suicide
According to the Michaelis-Menten model, kcat (turnover number) can be defined as the
maximum number of product molecules generated by a single enzyme over a specified time.
Metal ions, such as Fe2+ and Mg2+, that are required by an enzyme for its ability to function are called?
cofactors
Which enzyme mechanism involves the transfer of a proton from one molecule to another?
acid-base catalysis
True or False
Mixed is reversible by high [S]
False
Complex organic or metalloorganic molecules, such as lipoate or tetrahydrofolate, required for enzyme function are called
coenzymes.
What does the x intercept on a Lineweaver-Burk plot represent?
−1/Km
Why do allosteric enzymes display a sigmoid instead of a hyperbolic kinetics plot?
Modulator binding provokes cooperative interactions between multiple protein subunits.
What do isomerases do?
convert isomers
Name 2 features of the allosteric enzymes.
Modulators are usually heterotropic
Modulators bind non-covalently
Large, multisubunit enzymes are often allosteric.