1.The diagram below shows an outline of the aminotransferase mechanism that skips the specific steps that show how electrons flow when a Schiff base is formed or is hydrolyzed. Using the mechanistic details given below A. Draw the mechanism for Enzyme- PLP Schiff base formation using pyridoxal and the lysine amine group using arrow to indicate electron flow. B. Draw the mechanism for hydrolysis of the Schiff base to form the a-keto acid, which is the reverse of the first reaction. Stage 1 A. show how this forms Lys residue Lys residue H (CH)4 COO NH₂ Enz Amino acid H NH₂ R-C- -COO "NH₂ 2-0,PO- Enzyme-PLP Schiff base HO OH Pyridoxine (vitamin B₂) Amino acid-PLP Schiff base (aldimine) 2-O,PO- (CH2)4 NH₂ OH 2-O,PO OH 2-O,PO- Amino acid Pyridoxal phosphate (PLP) Ketimine H₂O a-Keto acid C-coo Pyridoxamine phosphate Stage 2 Stage 1 Lys residue 2-0,PO- Enz Enzyme-PLP Schiff base B. show how the a-keto acid forms a-Keto acid COO 2-0,PO- H COO NH₂ NH₂ R-C-COO NH3 2-0,PO- NH₂ Ketimine a-Keto acid C-coo (CH₂la NH₂ Enzyme-PLP Schiff base Figure 17.16 Amino acid-PLP Schiff base (aldimine) Biochemistry, First Edition, Copyright ©2017 W. W. Norton & Co., Inc. Ketimine 2-O,PO Pyridoxamine phosphate Other reagents can add as well. One group of compounds that adds is amines, substituted ammonia molecules with the general formula RNH₂. The reaction mechanism is very similar to those shown for the addition of H2O or alcohols. It is acid catalyzed. The first step of the mechanism generates a carbocation. This reacts with the lone pair of electrons on the nitrogen in the amine. The unstable product of this step is stabilized by the loss of an equivalent of water from the molecule, to form a Schiff base as shown below. step 1 (rate determining) [H] R R C=O+H-NH2- R *H* R R -Q-H HN-H Τ H R R step 2 H H R step 3 R H- H -O-H R-C-O-H + H+ H H R R - + H₂O H Schiff base
1.The diagram below shows an outline of the aminotransferase mechanism that skips the specific steps that show how electrons flow when a Schiff base is formed or is hydrolyzed. Using the mechanistic details given below A. Draw the mechanism for Enzyme- PLP Schiff base formation using pyridoxal and the lysine amine group using arrow to indicate electron flow. B. Draw the mechanism for hydrolysis of the Schiff base to form the a-keto acid, which is the reverse of the first reaction. Stage 1 A. show how this forms Lys residue Lys residue H (CH)4 COO NH₂ Enz Amino acid H NH₂ R-C- -COO "NH₂ 2-0,PO- Enzyme-PLP Schiff base HO OH Pyridoxine (vitamin B₂) Amino acid-PLP Schiff base (aldimine) 2-O,PO- (CH2)4 NH₂ OH 2-O,PO OH 2-O,PO- Amino acid Pyridoxal phosphate (PLP) Ketimine H₂O a-Keto acid C-coo Pyridoxamine phosphate Stage 2 Stage 1 Lys residue 2-0,PO- Enz Enzyme-PLP Schiff base B. show how the a-keto acid forms a-Keto acid COO 2-0,PO- H COO NH₂ NH₂ R-C-COO NH3 2-0,PO- NH₂ Ketimine a-Keto acid C-coo (CH₂la NH₂ Enzyme-PLP Schiff base Figure 17.16 Amino acid-PLP Schiff base (aldimine) Biochemistry, First Edition, Copyright ©2017 W. W. Norton & Co., Inc. Ketimine 2-O,PO Pyridoxamine phosphate Other reagents can add as well. One group of compounds that adds is amines, substituted ammonia molecules with the general formula RNH₂. The reaction mechanism is very similar to those shown for the addition of H2O or alcohols. It is acid catalyzed. The first step of the mechanism generates a carbocation. This reacts with the lone pair of electrons on the nitrogen in the amine. The unstable product of this step is stabilized by the loss of an equivalent of water from the molecule, to form a Schiff base as shown below. step 1 (rate determining) [H] R R C=O+H-NH2- R *H* R R -Q-H HN-H Τ H R R step 2 H H R step 3 R H- H -O-H R-C-O-H + H+ H H R R - + H₂O H Schiff base
Biochemistry
9th Edition
ISBN:9781319114671
Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Chapter1: Biochemistry: An Evolving Science
Section: Chapter Questions
Problem 1P
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Transcribed Image Text:1.The diagram below shows an outline of the aminotransferase mechanism that skips the specific steps that show how
electrons flow when a Schiff base is formed or is hydrolyzed. Using the mechanistic details given below
A. Draw the mechanism for Enzyme- PLP Schiff base formation using pyridoxal and the lysine amine group using arrow
to indicate electron flow.
B. Draw the mechanism for hydrolysis of the Schiff base to form the a-keto acid, which is the reverse of the first reaction.
Stage 1
Lys residue
2-O,PO-
Enz
Amino
acid
Lys residue
(CH2)4
(CH₂2)4
H
R-C-COO
R-
NH₂
NH₂
R-C-COO
*NH₂
H
H-
2-0,PO-
2-0,PO-
A. show how this forms
Stage 1
Lys residue
Enz
(CH2)4
HO
2-O,PO
Enzyme-PLP
Schiff base
OH
Amino acid-PLP
Schiff base
(aldimine)
LOH
2-0₂PO-
OH
20,PO-
a-Keto acid
COO
Ketimine
a-Keto acid
2-0,PO-
R-C-
NH₂
B. show how the a-keto acid
forms
a-Keto acid
H
Enzyme-PLP
Schiff base
الرواية وطري
Ketimine
Pyridoxine
(vitamin B6)
Pyridoxal
phosphate (PLP)
Pyridoxamine phosphate
Stage 2
Amino
acid
H
CH2)4
тран
H
(CH₂le
COO
NH₂
NH₂
R-C-COO
H
+NH
Enzyme-PLP
Schiff base
Figure 17.16
Amino acid-PLP
Schiff base
(aldimine)
Ketimine
Biochemistry, First Edition, Copyright ©2017 W. W. Norton & Co., Inc.
NH₂
NH₂
2-O,PO-
Pyridoxamine phosphate
Other reagents can add as well. One group of compounds that adds is amines, substituted ammonia molecules with the general formula RNH₂. The reaction mechanism is very similar to those shown
for the addition of H₂O or alcohols. It is acid catalyzed. The first step of the mechanism generates a carbocation. This reacts with the lone pair of electrons on the nitrogen in the amine. The unstable
product of this step is stabilized by the loss of an equivalent of water from the molecule, to form a Schiff base as shown below.
R
step 1
(rate determining)
C=O + H-NH2-
R
R
step 2
R
H-Ō
R-
H-N-H
step 3
Η ΤΗ
H
R
R-C-O-H
H-N-H
H
R
R-C-O-H + H+
H
H
H
R
R
R
you
R
+ H₂O
H
Schiff base
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