Organic Chemistry (8th Edition)
8th Edition
ISBN: 9780134042282
Author: Paula Yurkanis Bruice
Publisher: PEARSON
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Textbook Question
Chapter 23.5, Problem 15P
Explain why the ability of PLP to catalyze an amino acid transformation is greatly reduced if a PLP-requiring enzymatic reaction is carried out at a pH at which the pyridine nitrogen is not protonated.
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The first step in the catabolism of most amino acids is the removal of the nitrogen atom by transfer to an a-keto acid, a reaction
catalyzed by an enzyme called a transaminase. The a-keto acid acceptor is often a-ketoglutarate. Modify the structures in the
product to show the products of the transamination of cysteine. Be sure to show functional groups with the charge and number of
attached hydrogen atoms appropriate for pH 7.4.
transaminase
+
O=C
H₂N-CH
+
CH₂
CH₂
CH₂
SH
Incorrect
H₂N
||
CH
|
CH₂
|
CH₂
I
||
O
||
n
|
CH₂
T
SH
α-Amino acids can be prepared by treating an aldehyde with ammonia/trace acid, followed by hydrogen cyanide, followed by acid-catalyzed hydrolysis.
Draw the structures of the two intermediates formed in this reaction.
Use curved arrows to illustrate how the following decarboxylation occurs in the presence of an acid HA. This reaction constitutes one step in the biosynthesis of the amino acid tyrosine.
Chapter 23 Solutions
Organic Chemistry (8th Edition)
Ch. 23.1 - Prob. 2PCh. 23.1 - Prob. 3PCh. 23.2 - How many conjugated double bonds are there in a....Ch. 23.2 - Instead of adding to the 4a position and...Ch. 23.2 - Prob. 7PCh. 23.3 - Prob. 8PCh. 23.3 - Acetolactate synthase is another TPP-requiring...Ch. 23.3 - Acetolactate synthase transfers the acyl group of...Ch. 23.3 - Prob. 12PCh. 23.5 - Which compound is more easily decarboxylated?
Ch. 23.5 - Prob. 14PCh. 23.5 - Explain why the ability of PLP to catalyze an...Ch. 23.5 - Explain why the ability of PLP to catalyze an...Ch. 23.5 - The enzyme that catalyzes the C C bond cleavage...Ch. 23.5 - Propose a mechanism for the ,-elimination reaction...Ch. 23.6 - Ethanolamine ammonia lyase, a coenzyme...Ch. 23.6 - Prob. 20PCh. 23.7 - How do the structure of tetrahydrofolate and...Ch. 23.7 - What is the source of the methyl group in...Ch. 23.8 - Thiols such as ethanethiol and propanethiol can be...Ch. 23 - How does the metal ion in carboxypeptidase A...Ch. 23 - Prob. 24PCh. 23 - Prob. 25PCh. 23 - For each of the following reactions, name both the...Ch. 23 - Prob. 27PCh. 23 - When transaminated, the three branched-chain amino...Ch. 23 - What acyl groups have we seen transferred by...Ch. 23 - Propose a mechanism for the following reaction:Ch. 23 - Draw the products of the following reaction, where...Ch. 23 - When UMP is dissolved in T2O, exchange of T for H...Ch. 23 - Dehydratase is a PLP-requiring enzyme that...Ch. 23 - In addition to the reaction mentioned in Section...Ch. 23 - PLP can catalyze both ,-elimination reactions...Ch. 23 - The glycine cleavage system is a group of four...Ch. 23 - Prob. 37PCh. 23 - FADH2 reduces , -unsaturated thioesters to...
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