3. In your textbook the termi- nal enzyme catalyzing the ter- minal step of glycolysis is known as pyruvate kinase (PK). No indication is given that in mammalian tissues there are four different iso- forms of this enzyme. The four mammalian isoforms are known as PKL, PKR, PKM1 and PKM2. PKL is expressed in the liver, and PKR is ex- pressed in red blood cells. C PKM1 and PKM2 are derived from altemative splicing of the PKM gene. PKM1 is a constitu- tively active isoform expressed Active Site A PKM2 Monomer B Fructose-1,6-Bisphosphate N Phe, Ala, Ser Binding Site PKM2 Tetramer "Activator" Binding Site in differentiated cells from various tissues. In contrast, PKM2 has low basal activity and is activated by an effector molecule fructose 1,6-bisphosphate (FBP). PKM2 is expressed in most proliferating cells. In addition, the regulation of PKM2 pyruvate kinase activity plays an essential role in cancer metabolism and is crucial for the growth and survival of cancer cells. Recently, PKM2 has been reported to function also as a nuclear protein kinase to regulate gene transcription and promote tumorigenesis. The diagram on the right illustrates the quaternary structure of the PKM2 tetramer and the binding sites of metabolic effector molecules. (a) In the laboratory, the catalytic activity of pyruvate kinase is measured by a continuous assay coupled to lactate dehy-drogenase because the reaction products of the PK reac- tion have no suitable absorption or fluorescence properties, in contrast to the properties of NADH and NAD*, as shown in the diagram on the right. Write both reactions with structural for- mulas as a coupled system naming all metabolites, cofactors, and enzymes. Under what conditions in the cell do these reac- tions occur and why is this important for continued turnover of glycolysis? Optical density NAD+ NADH 250 300 350 wavelength (nm) 400

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
icon
Related questions
Question
3. In your textbook the termi-
nal enzyme catalyzing the ter-
minal step of glycolysis is
known as pyruvate kinase
(PK). No indication is given
that in mammalian tissues
there are four different iso-
forms of this enzyme. The four
mammalian isoforms are
known as PKL, PKR, PKM1
and PKM2. PKL is expressed
in the liver, and PKR is ex-
pressed in red blood cells. C
PKM1 and PKM2 are derived
from altemative splicing of the
PKM gene. PKM1 is a constitu-
tively active isoform expressed
Active Site
A
PKM2 Monomer
B
Fructose-1,6-Bisphosphate
N
Phe, Ala, Ser
Binding Site
PKM2 Tetramer
"Activator"
Binding Site
in differentiated cells from various tissues. In contrast, PKM2 has low basal activity and is activated by
an effector molecule fructose 1,6-bisphosphate (FBP). PKM2 is expressed in most proliferating cells.
In addition, the regulation of PKM2 pyruvate kinase activity plays an essential role in cancer metabolism
and is crucial for the growth and survival of cancer cells. Recently, PKM2 has been reported to function
also as a nuclear protein kinase to regulate gene transcription and promote tumorigenesis. The diagram
on the right illustrates the quaternary structure of the PKM2 tetramer and the binding sites of metabolic
effector molecules.
(a) In the laboratory, the catalytic activity of pyruvate
kinase is measured by a continuous assay coupled to lactate
dehy-drogenase because the reaction products of the PK reac-
tion have no suitable absorption or fluorescence properties, in
contrast to the properties of NADH and NAD*, as shown in the
diagram on the right. Write both reactions with structural for-
mulas as a coupled system naming all metabolites, cofactors,
and enzymes. Under what conditions in the cell do these reac-
tions occur and why is this important for continued turnover of
glycolysis?
Optical density
NAD+
NADH
250
300
350
wavelength (nm)
400
Transcribed Image Text:3. In your textbook the termi- nal enzyme catalyzing the ter- minal step of glycolysis is known as pyruvate kinase (PK). No indication is given that in mammalian tissues there are four different iso- forms of this enzyme. The four mammalian isoforms are known as PKL, PKR, PKM1 and PKM2. PKL is expressed in the liver, and PKR is ex- pressed in red blood cells. C PKM1 and PKM2 are derived from altemative splicing of the PKM gene. PKM1 is a constitu- tively active isoform expressed Active Site A PKM2 Monomer B Fructose-1,6-Bisphosphate N Phe, Ala, Ser Binding Site PKM2 Tetramer "Activator" Binding Site in differentiated cells from various tissues. In contrast, PKM2 has low basal activity and is activated by an effector molecule fructose 1,6-bisphosphate (FBP). PKM2 is expressed in most proliferating cells. In addition, the regulation of PKM2 pyruvate kinase activity plays an essential role in cancer metabolism and is crucial for the growth and survival of cancer cells. Recently, PKM2 has been reported to function also as a nuclear protein kinase to regulate gene transcription and promote tumorigenesis. The diagram on the right illustrates the quaternary structure of the PKM2 tetramer and the binding sites of metabolic effector molecules. (a) In the laboratory, the catalytic activity of pyruvate kinase is measured by a continuous assay coupled to lactate dehy-drogenase because the reaction products of the PK reac- tion have no suitable absorption or fluorescence properties, in contrast to the properties of NADH and NAD*, as shown in the diagram on the right. Write both reactions with structural for- mulas as a coupled system naming all metabolites, cofactors, and enzymes. Under what conditions in the cell do these reac- tions occur and why is this important for continued turnover of glycolysis? Optical density NAD+ NADH 250 300 350 wavelength (nm) 400
Expert Solution
trending now

Trending now

This is a popular solution!

steps

Step by step

Solved in 2 steps

Blurred answer
Similar questions
  • SEE MORE QUESTIONS
Recommended textbooks for you
Biochemistry
Biochemistry
Biochemistry
ISBN:
9781319114671
Author:
Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Publisher:
W. H. Freeman
Lehninger Principles of Biochemistry
Lehninger Principles of Biochemistry
Biochemistry
ISBN:
9781464126116
Author:
David L. Nelson, Michael M. Cox
Publisher:
W. H. Freeman
Fundamentals of Biochemistry: Life at the Molecul…
Fundamentals of Biochemistry: Life at the Molecul…
Biochemistry
ISBN:
9781118918401
Author:
Donald Voet, Judith G. Voet, Charlotte W. Pratt
Publisher:
WILEY
Biochemistry
Biochemistry
Biochemistry
ISBN:
9781305961135
Author:
Mary K. Campbell, Shawn O. Farrell, Owen M. McDougal
Publisher:
Cengage Learning
Biochemistry
Biochemistry
Biochemistry
ISBN:
9781305577206
Author:
Reginald H. Garrett, Charles M. Grisham
Publisher:
Cengage Learning
Fundamentals of General, Organic, and Biological …
Fundamentals of General, Organic, and Biological …
Biochemistry
ISBN:
9780134015187
Author:
John E. McMurry, David S. Ballantine, Carl A. Hoeger, Virginia E. Peterson
Publisher:
PEARSON