a) List and draw the structure of this coenzyme. Which of the coenzymes required by the PDH does this molecular analog displace? b) coenzyme? How does the transition state analog differ chemically from the naturally occurring b) activity? This can be illustrated by drawing the reactions, in words, or both. Why would the chemical difference, described in part b, result in a loss of PDH enzyme

Which of the following statements about de novo purine synthesis is true? (A) Purine nucleotides are formed by separately synthesizing the phosphorylated ribose and the purine ring and then joining them together.(B) GMP is formed first and is used as a precursor to form AMP.(C) The synthesis of AMP from inosinate is driven forward by ATP hydrolysis. (D) GMP synthetase uses NADPH and glutamine to modify the inosinate ring to form GMP.(E) Replacement of the C-1 PPi on PRPP with an amine is required to construct the purine ring on the ribose sugar.

Phosphoglycerate mutase transfers a phosphoryl group from C3 of 3-phosphoglycerate to C2  position to give 2-phosphoglycerate. Why is it important to have the phosphoryl group at  position 2 rather than at C3? It was observed that the activity of some preparations of the  enzyme could be increased if catalytic (very small) amount of 2, 3-bisphosphoglycerate was  added to the enzyme. Give a possible explanation for this observation.

If G6P is labeled at its C2 position, where will the label appear in the products of the pentose phosphate pathway?

You are studying the kinetics of a novel competitive inhibitor of ATP-citrate lyase that can be used to prevent obesity. What is likely true about this inhibitor? (A) This inhibitor lowers the Vmax of ATP-citrate lyase. (B) The inhibitor likely looks structurally similar to acetyl CoA. (C) The inhibitor binds to an allosteric region on ATP-citrate lyase and prevents catalysis. (D) You can distinguish between an uninhibited and inhibited enzyme by comparing the x-intercepts on a Lineweaver-Burk plot. (E) This inhibitor lowers the KM of ATP-citrate lyase. Related to this question, you should also be able to: • explain the function of ATP-citrate lyase and why inhibition would prevent obesity • interpret Michaelis-Menten & Lineweaver-Burk plots related to this question • explain the differences between a competitive and non-competitive inhibitor

Coenzyme-dependent enzymes can catalyze the general transformations shown below.What would be the best coenzymes to use for the two steps in the scheme, and why? Then, proposean enzyme-catalyzed method for step A to proceed without a coenzyme. Show this enzymecatalyzed mechanism for step A that does not require the coenzyme. You can abbreviate acidicamino acid residues “Enz–B–H” and basic residues “ B–Enz”.

PLP is a cofactor for a number of enzymes involved in amino acid metabolism. Give an example of reaction in which PLP participates in cleavage of the a, b, and c bonds of an amino acid, as diagrammed in shown Fig.

Which of the following intermediates of the TCA cycle has 5 carbons? (Hint: You don't need to have memorized specific structures for this question, just recall what molecules the TCA cycle starts with and where in the cycle carbons are lost as CO2 ).  a) Fumarate b) None of the above  c) Succinyl CoA d) Citrate e) Oxaloacetate

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.

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