FIGURE 30-5 Cofactors and coenzymes (a) Metal ion cofactors (Mg2+) stabilize the carboxylate portion of 2-phosphoglycerate in the active site of the enzyme enolase. (b) Nicotinamide adenine dinucleotide is a coenzyme that can exist in its oxidized form (NAD+) or its reduced form (NADH). Rib represents a ribose sugar unit, and ADP represents an attached adenosine diphosphate group. (a) (b) ADP Rib ADP Rib N Reduction Oxidation H H NH₂ H H NH2 O-H Lys-345 NH₂ Mg2+ Mg2+ - ότ O=P- H O=C Glu-211 NAD+ + H+ + 2e¯ NADH

FIGURE 30-5 Cofactors and coenzymes (a) Metal ion cofactors (Mg2+) stabilize the carboxylate portion of 2-phosphoglycerate in the active site of the enzyme enolase. (b) Nicotinamide adenine dinucleotide is a coenzyme that can exist in its oxidized form (NAD+) or its reduced form (NADH). Rib represents a ribose sugar unit, and ADP represents an attached adenosine diphosphate group. (a) (b) ADP Rib ADP Rib N Reduction Oxidation H H NH₂ H H NH2 O-H Lys-345 NH₂ Mg2+ Mg2+ - ότ O=P- H O=C Glu-211 NAD+ + H+ + 2e¯ NADH

Biochemistry

6th Edition

ISBN:9781305577206

Author:Reginald H. Garrett, Charles M. Grisham

Publisher:Reginald H. Garrett, Charles M. Grisham

Chapter27: Metabolic Integration And Organ Specialization

Section: Chapter Questions

Problem 20P: Figure 27.3 illustrates the response of R (ATP-regenerating) and U (ATP-utilizing) enzymes to energy...

See similar textbooks

Similar questions

Using the ActiveModel for enoyl-CoA dehydratase, give an example of a case in which conserved residues in slightly different positions can change the catalytic rate of reaction.
The Reactions and Meehanisms of the Leloir Pathway Write the reactions that permit galactose to be utilized in glycolysis. Write a suitable mechanism, tor one of these reactions.
Using the ActiveModel for aldose reductase, describe the structure of the TIM barrel motif and the structure and location of the active site.
Examine the ActiveModel for alcohol dehydrogenase and describe the structure and function of the catalytic zinc center.
Distinguishing the Mechanisms of Class I and Class I Aldolases Fructose bisphosphate aldolase in animal muscle is a class 1 aldolase, which forms a Schiff base intermediate between substrate (for example. fructose-1, 6-bisphosphate or dihydroxyacetone phosphate) and a lysine at the active site (see Figure I8.12). The chemical evidence for this intermediate conies from studies with aldolase and the reducing agent sodium borohydride, NaBH4. Incubation of the enzyme with dihydroxyacetone phosphate and NaBH4 inactivates the enzyme. Interestingly, no inactivation is observed if NabH4 is added to the enzyme in the absence of substrate. Write a mechanism that explains these observations and provides evidence for the formation of a Schiff base intermediate in the aldolase reaction.
How Do Vitamin-Derived Coenzymes Aid Metabolism? What chemical functionality is provided to enzyme reactions by pyridoxal phosphate (we Chapter 13)? By coenzyme A (see Chapter I9)? By vitamin B12 (see Chapter 23)? By thiamine pyrophosphate (see Chapter 19)?
Complete oxidation of a 16-carbon fatty acid can yield 129 molecules of ATP Study Figure 19.2 and determine how many ATP molecules would be generated if a 16-carbon fatly acid were metabolized solely by the TCA cycle, in the form of S acetyl-CoA molecules.
Both prokaryotic and eukaryotic organisms carry out some form of glycolysis. How does ha fact support or not support the assertion that glycolysis is one of the oldest metabolic pathways?
Understanding the Mechanism of Hemolytic Anemia Genetic defects in glycolytic enzymes can have serious consequences for humans For example, defects in the gene for pyruvate kinase can result in a condition known as hemolytic anemia. Consult a reference to learn about hemolytic anemia, and discuss why such genetic defects lead to this condition.
Understanding Enzyme Mechanisms Related to Pyruvate Carboxylase Based on the mechanism for pyruvate carboxylase (Figure 22.3), write reasonable mechanisms for the reactions that follow:
Ethanol as a Source of Metabolic Energy (Integrates with Chapters 19 and 20.) Acetate produced in ethanol metabolism can be transformed into acetyl-COA by the acetyl thiokinase reaction: Acetate+ATP+CoASHacetyleCoA+AMP+PPiAcetyle-CoA then can enter the citric acid cycle and undergo oxidation to 2 CO2by this route, assuming oxidative phosphorylation is part of the process? (Assume all reactions prior to acetyl-CoA entering the citric acid cycle occur outside the mitochondrion). Per carbon atom, which is a better metabolic fuel, ethanol or glucose? That is, how many ATP equivalents per carbon atom are generated by combustion of glucose versus ethanol to CO2?
Why Do Anabolic and Catabolic Pathways Differ? Why is the pathway for the biosynthesis of a biomolecule at least partially different from the pathway for its catabolism? Why is the pathway for the biosynthesis of a biomolecule inherently more complex than the pathway for its degradation?