Organic Chemistry (8th Edition)
8th Edition
ISBN: 9780134042282
Author: Paula Yurkanis Bruice
Publisher: PEARSON
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Chapter 26, Problem 33P
RNAase, the enzyme that catalyzes the hydrolysis of RNA, has two catalytically active histidine residues at its active site. One of the histidine residues is catalytically active in its acidic form, and the other is catalytically active in its basic form. Propose a mechanism for RNAase.
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Question 1
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Chapter 26 Solutions
Organic Chemistry (8th Edition)
Ch. 26.1 - In acidic solutions, nucleosides are hydrolyzed to...Ch. 26.1 - Draw the structure for each of the following: a....Ch. 26.3 - Indicate whether each functional group of the five...Ch. 26.3 - Prob. 4PCh. 26.3 - If one of the strands of DNA has the following...Ch. 26.4 - The 2',3-cyclic phosphodiester that is formed...Ch. 26.5 - Using a dark line for the original parental DNA...Ch. 26.7 - Why do both thymine and uracil specify the...Ch. 26.9 - If methionine is always the first amino acid...Ch. 26.9 - Four Cs occur in a row in the segment of mRNA...
Ch. 26.9 - UAA is a stop codon. Why does the UAA sequence in...Ch. 26.9 - Prob. 12PCh. 26.9 - Write the sequences of bases in the sense strand...Ch. 26.9 - List the possible codons on mRNA that speciy each...Ch. 26.10 - Adenine can be deaminated to hypoxanthine, and...Ch. 26.10 - Explain why thymine cannot be deaminated.Ch. 26.12 - Which of the following base sequences is most...Ch. 26 - What nonapeptide is coded for by the following...Ch. 26 - What is the sequence of bases in the template...Ch. 26 - Prob. 20PCh. 26 - A segment of DNA has 18 base pairs. It has 7...Ch. 26 - Name the following:Ch. 26 - Prob. 23PCh. 26 - Propose a mechanism for the following reaction:Ch. 26 - The first amino acid incorporated into a...Ch. 26 - Match the codon with the anticodon:Ch. 26 - a. Using the single-letter abbreviations for the...Ch. 26 - Which of the following pairs of dinucleotides are...Ch. 26 - Human immunodeficiency virus (HIV) is the...Ch. 26 - If a mRNA contained only U and G in random...Ch. 26 - Why is the codon a triplet rather than a doublet...Ch. 26 - RNAase, the enzyme that catalyzes the hydrolysis...Ch. 26 - The amino acid sequences of peptide fragments...Ch. 26 - Which cytosine in the following sense strand of...Ch. 26 - Prob. 36PCh. 26 - Sodium nitrite, a common food preservative (page...Ch. 26 - Why does DNA not unravel completely before...Ch. 26 - Staphylococcus nuclease is an enzyme that...
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- On complete hydrolysis, a polypeptide gives two alanine, one leucine, one methionine, one phenylalanine, and one valine residue. Partial hydrolysis gives the following fragments: Ala-Phe, Leu-Met, Val-Ala, Phe-Leu. It is known that the first amino acid in the sequence is valine and the last one is methionine. What is the complete sequence of amino acids?arrow_forwardAmine bases in nucleic acids can react with alkylating agents in typical SN2 reactions. Look at the following electrostatic potential maps, and tell which is the better nucleophile, guanine or adenine. The reactive positions in each are indicated.arrow_forwardThe following data were recorded from an experiment to measure the activity of a peptidase enzyme. A number of solutions of different concentrations of a dipeptide were prepared then the same small amount of the enzyme was added to each of them. The rate of cleavage of the peptide bond was measured and the initial rate of the reaction was recorded Peptide conc (mmol L-¹) 0.334 0.450 0.667 1.00 1.33 1.67 Initial rate 0.152 0.201 0.269 0.417 0.505 0.667 (mmol L¹ s¹) For the peptidase enzyme find the maximum velocity and the Michaelis constant.arrow_forward
- The enzyme that catalyzes the Ca ¬ Cb bond cleavage reaction that converts serine to glycine removes thesubstituent (R) bonded to the a-carbon in the first step of the reaction. Starting with PLP bound to serine inan imine linkage, propose a mechanism for this reaction. (Hint: The first step involves removal of the protonfrom serine’s OH group.)arrow_forward(a) An aliphatic aminoglycoside is relatively stable to base, but it is quickly hydrolyzed bydilute acid. Propose a mechanism for the acid-catalyzed hydrolysis.NHHCH2RR2NH2 + sugarRHHOH OHOH Oan aliphatic ribosideH3O+ +(b) Ribonucleosides are not so easily hydrolyzed, requiring relatively strong acid.Using your mechanism for part (a), show why cytidine and adenosine (for example)are not so readily hydrolyzed. Explain why this stability is important for livingorganisms.arrow_forwardExposure to nitrous acid (see Section 19-16), sometimes found in cells, can convert cytosine to uracil.(a) Propose a mechanism for this conversion.(b) Explain how this conversion would be mutagenic upon replication.(c) DNA generally includes thymine, rather than uracil (found in RNA). Based on this fact, explain why the nitrous-acidinduced mutation of cytosine to uracil is more easily repaired in DNA than it is in RNA.*arrow_forward
- Chorismate mutase is an enzyme that promotes a pericyclic reaction by forcing the substrate to assume the conformation needed for the reaction. The product of the pericyclic reaction is prephenate that is subsequently converted into the amino acids phenylalanine and tyrosine. What kind of a pericyclic reaction does chorismate mutase catalyze?arrow_forwardAn octapeptide contains the following amino acids: Arg, Glu, His, Ile, Leu, Phe, Tyr, and Val. Carboxypeptidase treatment of the octapeptide forms Phe and a heptapeptide. Treatment of the octapeptide with chymotrypsin forms two tetrapeptides, A and B. Treatment of A with trypsin yields two dipeptides, C and D. Edman degradation cleaves the following amino acids from each peptide: Glu (octapeptide), Glu (A), Ile (B), Glu (C), and Val (D). Partial hydrolysis of tetrapeptide B forms Ile–Leu in addition to other products. Deduce the structure of the octapeptide and fragments A–D.arrow_forwardDraw a diagram of the linear and ring structures of ribose. Show the biochemical mechanism of cyclization of each and name the resultant ring – including the ring type & anomeric carbon designation. Draw and name an amine version, reduced version, and oxidized version, either in ring or Fisher projection.arrow_forward
- During base excision repair, DNA glycosylase cleaves theN-glycosidic link between the altered base and the deoxyribose component of the nucleotide. Draw a typical nucleotideand indicate which bond is cleaved.arrow_forwardO alanine glycine Ovaline Oleucine O isoleucine HN Leucine Alanine 1. Excess NH,+ trace acid 3. HC, H₂O + heat Glyche Alm Mis holmainearrow_forwardRetroviruses like HIV, the pathogen responsible for AIDS, incorporate an RNA template that is copied into DNA duringinfection. The reverse transcriptase enzyme that copies RNA into DNA is relatively nonselective and error-prone, leadingto a high mutation rate. Its lack of selectivity is exploited by the anti-HIV drug AZT (3′@azido@2′,3′@dideoxythymidine),which becomes phosphorylated and is incorporated by reverse transcriptase into DNA, where it acts as a chain terminator.Mammalian DNA polymerases are more selective, having a low affinity for AZT, so its toxicity is relatively low.(a) Draw the structures of AZT and natural deoxythymidine.(b) Draw the structure of AZT 5′@triphosphate, the derivative that inhibits reverse transcriptase.*2arrow_forward
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