What if C-1 of the oxaloacetate were labeled instead, when would the label be released as CO2?
What if C-1 of the oxaloacetate were labeled instead, when would the label be released as CO2?
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
Related questions
Question
What if C-1 of the oxaloacetate were labeled instead, when would the label be released as CO2?
Transcribed Image Text:(a) Fate of the carboxyl carbon of acetate unit
HO-
Oxaloacetate
Malate
Fumarate
Oxaloacetate
HO-O
00
Malate
Fumarate
Succinate
6-77
10-47
33
Malate
49
Oxaloacetate
Fumarate
Succinyl-CoA
(b) Fate of methyl carbon of acetate unit
O-S-Col
Succinate
-S-CoA
HO-O
1st turn
1st turn
Succinate
HO-C
Citrate
HO-
3rd turn
Succinyl-CoA
HO-
a-Ketoglutarate
Citrate
Isocitrate
но-
a-Ketoglutarate
Citrate
Succinyl-CoA
Isocitrate
HO-
Isocitrate
a-ketoglutarate
O
(100₂)
O
00₂)
(00₂)
(CO₂)
(00₂)
(CO₂)
½ Total
methyl C
label
O
Oxaloacetate
HO-O-O
Malate
Fumarate
HO-G
0-7-7
Malate
Oxalcacetate
Fumarate
0-8-s-coA
HO-9
23
Malate
29
Succinate
Fumarate
029
99
Oxaloacetate
2nd turn
HO-
0-8--0
Succinate
Succinyl-COA
2nd turn
110-
Succinate
0-8-s-c
Citrate
10-
4th turn
Succinyl-CoA
a-Ketoglutarate,
Citrate
HO
Isocitrate
HO-
a-Ketoglutarate
Succinyl-CoA
Citrate
HO
Isocitrate O
(100₂)
Isocitrate
a-Ketoglutarate
(00₂)
(CD)
(00₂)
↑
(CO₂),
All labeled
carboxyl carbon
removed by these
two steps
Total
methyl C
label
Expert Solution
Step 1: Oxaloacetate
Oxaloacetate is a four-carbon compound, and carbon-1 (C-1) refers to the first carbon atom in the molecule. When oxaloacetate undergoes a series of reactions in the citric acid cycle (also known as the Krebs cycle or TCA cycle), it eventually loses carbon atoms in the form of carbon dioxide (CO2). However, the specific carbon atom labeled as C-1 would not be released as CO2 until several steps into the cycle.
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