Refer to the reaction scheme of the GAPDH catalyzed formation of 1,3-BPG. In the reaction, the nucleophile in step (4) is an inorganic phosphate molecule. The enzyme active site is elaborately constructed so that inorganic phosphate, not water, acts as the nucleophile. What advantage is gained by using inorganic phosphate, instead of water, as the nucleophile? Discuss in terms of the energy yield of glycolysis. No need to calculate the total net energy yield of glycolysis.
Refer to the reaction scheme of the GAPDH catalyzed formation of 1,3-BPG. In the reaction, the nucleophile in step (4) is an inorganic phosphate molecule. The enzyme active site is elaborately constructed so that inorganic phosphate, not water, acts as the nucleophile. What advantage is gained by using inorganic phosphate, instead of water, as the nucleophile? Discuss in terms of the energy yield of glycolysis. No need to calculate the total net energy yield of glycolysis.
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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Refer to the reaction scheme of the GAPDH catalyzed formation of 1,3-BPG. In the reaction, the nucleophile in step (4) is an inorganic phosphate molecule. The enzyme active site is elaborately constructed so that inorganic phosphate, not water, acts as the nucleophile.
What advantage is gained by using inorganic phosphate, instead of water, as the nucleophile? Discuss in terms of the energy yield of glycolysis. No need to calculate the total net energy yield of glycolysis.
Transcribed Image Text:CH,OPO3
NAD+
NAD+
Glyceraldehyde
3-phosphate
НСОН
H'
Glyceraldehyde
3-phosphate
dehydrogenase
Formation of enzyme-
substrate complex. The
active-site Cys has a reduced
pk, (5.5 instead
of 8) when NAD+ is bound,
and is in the more reactive,
thiolate form.
Сys
Cys
A covalent thiohemiacetal
linkage forms between the
substrate and the -S
group of the Cys residue.
NAD
ÇH,OPO?
НСОН
ÇH,OPO3
The covalent thioester
linkage between the
substrate and enzyme
undergoes phosphorolysis
(attack by P;) releasing the
second product, 1,3-
bisphosphoglycerate.
НСОН
O TH
C=0
OPo?
2-
Cys
The enzyme-substrate
intermediate is oxidized by
the NAD+ bound to the
1,3-Bisphosphoglycerate
active site.
CH,OPO?
НСОН
NAD+
CH,OPO}
NADH
Pi NAD+
НСОН
C=0
C=0
NADH
The NADH product leaves the
active site and is replaced by
another molecule of NAD+.
Сys
Figure 14-7
Lehninger Principles of Biochemistry, Fifth Edition
© 2008 W. H. Freeman and Company
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