Which of the following enzymes mentioned in the chapter was the first to be crystallized, providing early evidence that enzymes were proteins?
Explanation
The crystallization of the enzyme urease by James Sumner in 1926 was a pivotal moment in the history of biochemistry. It provided the first strong experimental evidence that enzymes were, in fact, proteins, a controversial idea at the time.
Other questions
What is the term for a complete, catalytically active enzyme together with its bound coenzyme and/or metal ions?
According to the international classification system, what type of reaction is catalyzed by enzymes in Class 2?
What is the primary function of a catalyst in a chemical reaction like S to P?
What is the primary source of the free energy used by enzymes to lower the activation energies of reactions?
According to the principles of enzymatic catalysis, an enzyme's active site is most complementary to what part of the reaction it catalyzes?
In the Michaelis-Menten equation, what does the term Km represent?
What type of plot is created when plotting the reciprocal of initial velocity (1/V0) versus the reciprocal of substrate concentration (1/[S])?
For an enzyme-catalyzed reaction, the turnover number, kcat, is 500 per second. If the total enzyme concentration [Et] is 10 nM, what is the Vmax?
What kinetic parameter is considered the best measure for comparing the catalytic efficiencies of different enzymes or the turnover of different substrates by the same enzyme?
How does a competitive inhibitor affect the kinetic parameters of an enzyme-catalyzed reaction?
What is a distinguishing characteristic of an uncompetitive inhibitor?
In the chymotrypsin mechanism, which three amino acid residues form the catalytic triad?
What is the role of the 'oxyanion hole' in the chymotrypsin mechanism?
The mechanism of hexokinase, which involves a conformational change upon substrate binding, is a classic example of what concept?
What is the term for a regulatory enzyme's behavior where the substrate itself acts as a modulator?
Allosteric enzymes typically display what kind of kinetic behavior when plotting initial velocity (V0) versus substrate concentration ([S])?
What is a common method of enzyme regulation that involves the cleavage of a peptide bond in an inactive precursor?
Which of the following is an example of a suicide inactivator, a class of irreversible inhibitors?
The rate enhancement for the enzyme carbonic anhydrase is 10 to the power of 7. If the catalyzed reaction takes 1 second, approximately how long would the uncatalyzed reaction take?
Which type of enzyme regulation is generally irreversible?
For the enzyme hexokinase from brain, which substrate has the lowest Km value, indicating the highest affinity?
Which enzyme listed has the highest turnover number (kcat), representing the fastest conversion of substrate to product at saturation?
An enzyme is said to have achieved 'catalytic perfection' when its kcat/Km ratio approaches what range?
In a bisubstrate reaction with a Ping-Pong mechanism, what is a key feature of the reaction sequence?
What type of catalysis involves the transfer of a proton by a weak acid or base other than water?
The enzyme carbonic anhydrase has a kcat/Km of 8.3 x 10^7 per Molar per second for its substrate CO2. What does this value suggest about the enzyme's efficiency?
What type of enzyme is responsible for the regulation of many others by catalyzing the attachment of phosphoryl groups to them?
The first experimental evidence for a covalent acyl-enzyme intermediate in the chymotrypsin mechanism came from observing what phenomenon during the hydrolysis of p-nitrophenylacetate?
Beta-lactamase is an enzyme produced by resistant bacteria that inactivates penicillin. What kind of compounds were developed to irreversibly inactivate beta-lactamases?
What is the consequence of a reaction having a rate constant k of 0.03 per second?
How do molecules designed as transition-state analogs act as potent enzyme inhibitors?
What is the typical pH-activity profile for an enzyme like chymotrypsin when its rate is measured over a wide pH range?
Which of the following describes the first step of the lysozyme reaction in the SN2 (covalent catalysis) mechanism?
What is the primary role of metal ions, such as the two Mg2+ ions, in the enolase reaction mechanism?
In the blood coagulation cascade, what is the role of proteases like thrombin?
The enzyme chymotrypsin is a member of which class of enzymes?
What is the key difference between a coenzyme and a prosthetic group?
An enzyme with a Km of 0.0050 M is operating at a substrate concentration of 0.0050 M. What is its velocity as a fraction of Vmax?
In the catalytic triad of chymotrypsin, His57 has an unusually high pKa of 12. What is the functional consequence of this?
Which statement best describes the kinetic effect of a mixed inhibitor on an enzyme?
The regulation of glycogen phosphorylase involves both phosphorylation and allosteric modulation. This multi-level control is an example of what principle?
If a mutation in an allosteric enzyme causes its V0 versus [S] curve to shift from sigmoidal to hyperbolic, what has likely been lost?
The digestive enzyme trypsin is specific for cleaving peptide bonds on the carboxyl side of which amino acid residues?
A reaction rate is increased by a factor of 100,000. By how much must the activation energy (delta G double dagger) be lowered to achieve this, at cellular temperatures?
What is the general term for the inactive precursor of an enzyme, such as trypsinogen for trypsin?
If an enzyme-catalyzed reaction is in the pre-steady state, what is occurring?
The active site of an enzyme often sequesters a substrate from aqueous solution. This desolvation contributes to catalysis primarily by:
What type of consensus sequence is recognized by protein kinase A (PKA) for phosphorylation?
The blood coagulation cascade is an example of a mechanism that allows for what important feature of a signaling process?