An enzyme with an unknown reaction mechanism has been isolated and is being investigated in the lab. Based on the information given below, propose one or more specific catalytic strategies (covalent, acid-base, and/or metal ion catalysis) used by the enzyme and predict the role of each catalytic residue in the enzyme's reaction cycle. Explain your reasoning. (a) Mapping of the active site with substrate analog showed that it contains a critical Ser residue. (b) Studies conducted in buffers of varying pH showed that the enzyme is sensitive to pH changes and has two catalytically important residues with pKa values of ~10.5 and ~4.0. (c) Substitution of the Ser residue with Ala resulted in a five-fold increase in the KM but had no effect on the kcat. (d) The reaction rate was insensitive to the addition of metal chelators such as EDTA and EGTA.

A mixed inhibitor of an enzyme (sometimes called a mixed non-competitive inhibitor) can decrease the rate of a reaction by any of the following EXCEPT by: a) binding to a site other than the active site of the enzyme. b) binding to the active site of the enzyme, preventing substrate binding. c) decreasing kcat. d) Increasing KM.

It's a three part question based on the chart provided asking: a) Which of these enzymes has the weakest binding of substrate? (I chose fumarase since it has lowest Km but that was wrong so I don't understand) b) Which enzyme has the fastest conversion of ES? (I would assume this means highest Kcat value, so should be catalase) c) Which enzyme is most closely catalytically perfect? (I'm assuming this means highest Kcat/Km ratio, so I was thinking Crotonase, although I don't know what classifies an enzymes as 'catalytically perfect', please explain)

What are enzymes? What distinguishes enzymes from regular chemical catalysts? On the specificity of enzyme action, please comment. Which factor accounts for their specificity the most? Describe the enzyme catalysis mechanism.

Enzyme Y follows Michaelis-Menten kinetics. Km of the enzyme for Substrate A is 12 mM and for substrate B is 26 mM. The rate constant k2 with substrate A is 1x10 sec". With substrate B, k2 is 4x10 sec". Which substrate, substrate A or substrate B, will the enzyme use with greater catalytic efficiency? Explain your answer.

The value of Vmax for an enzyme-catalyzed reaction: A) most often reflects the chemical steps of catalysis B) can be determined from initial velocities that are linear with respect to substrate concentration OC) is limited only by the amount of substrate supplied D) can be converted to kcat/Km by accounting for the enzyme concentration OE) is higher for enzymes that also exhibit higher Km values

How will a graph of reaction rate (V) vs. [substrate] for an allosteric enzyme differ from the hyperbolic plot characteristic of enzymes having Michaelis-Menten kinetics?

Given the following reaction and equation for the initial velocity of the reaction: k₁ k3 E+S ES E + P V=Keat [ES] = k3 [ES] k₂ where keat is the rate constant for the reaction which forms the product from the ES complex. Explain in words why the velocity is directly proportional to theamount of enzyme added in the presence of saturating substrate levels.

Does the enzyme described in each of the following statementsrequire a cofactor to be active?(a) Ni2+ is present in the active site.(b) Addition of FAD allows the reaction to occur.(c) The presence of K+ does not affect the reaction.

The enzyme pyruvate carboxylase is discovered in a bacterium that was thought not to contain it; in this case study, you’ll see how researchers study and characterize the enzyme, and, ultimately, show how it fits into a metabolic pathway. Following purification of the PYC enzyme by avidin-Sepharose affinity chromatography, the investigators carried out several experiments to characterize the enzyme. First, they ran samples of the enzyme on denaturing and non-denaturing gels; the results are shown in the figure to the right. In addition, they ran the protein through a calibrated gel filtration column, the results of which indicated that the PYC enzyme had a molecular weight of 540 kiloDaltons. In the figure, the rightmost column are where molecular weight standards of various sizes would occur if they’d been on the gels. Part A: There are four identical subunits in the PYC enzyme. And there are not four domains in the denaturing gel. Based on the image provided attached, how many chains…