Biochemistry
6th Edition
ISBN: 9781305577206
Author: Reginald H. Garrett, Charles M. Grisham
Publisher: Cengage Learning
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Chapter 24, Problem 20P
Interpretation Introduction
Interpretation:
A series of steps or a cycle of reactions that could achieve the enrichment of phosphatidylinositol with 1-stearoyl-2-archidonoyl phosphatidylinositol needs to be proposed.
Concept Introduction:
The phosphatidylinositol cycle involves in cell signaling. Its major purpose is to synthesize phosphatidylinositol and its phosphorylated forms. The lipid intermediate of PI cycle are highly enriched with 1-stearoyl-2-arachidnoyl molecular species. This enrichment is retained as long as the intermediates are segregated from other lipids. What happens in the enrichment of a particular phospholipid molecule is selective addition of one specific type of alkyl or the acyl chain. There are several enzymes that involve in the conversion of phospholipids to exhibit specific acyl or alkyl chains.
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The venom of the Eastern diamondback rattler and the Indian cobra contains phospholipase A2, which catalyzes the hydrolysis of fatty acids at the C-2 position of glycerophospholipids. The phospholipid breakdownproduct of this reaction is lysolecithin (lecithin is phosphatidylcholine). At high concentrations, this and other lysophospholipids act as detergents, dissolving the membranes of erythrocytes and lysing the cells. Extensive hemolysis may be lifethreatening.(a) All detergents are amphipathic. What are the hydrophilic and hydrophobic portions of lysolecithin?(b) The pain and inflammation caused by a snake bite can be treated with certain steroids. What is the basis of this treatment?(c) Though the high levels of phospholipase A2 in venom can be deadly, this enzyme is necessary for a variety of normal metabolic processes. What are these processes?
Some of the following four amino acids :
alanine, arginine, histidine, aspartic acid would
provide a side chain for acid-base catalysis at
physiological pH (assume pK of each amino acid
is equal to pK value for the free amino acid in
solution).
Explain for each amino acid how and why each
would or would not provide the side chain
residue to support acid-base catalysis at
physiological pH.
Sphingosine 1-phosphate (SPP) is important for cell survival. The synthesis of SPP from sphingosine and ATP is catalyzed by the enzyme sphingosine kinase. An understanding of the kinetics of the sphingosine kinase reaction may be important in the development of drugs to treat cancer. The velocity of the sphingosine kinase reaction was measured in the presence and absence of threo-sphingosine, a stereoisomer of sphingosine that inhibits the enzyme. The results are shown below
.[Sphingosine], μM
2.5
3.5
5
10
20
50
v0(mg·minꟷ1) no inhibitor
32.3
40
50.872
87.7
115.4
v0(mg·minꟷ1)with threo-sphingosine
8.5
11.5
14.6
25.4
43.9
70.8
Construct a Lineweaver-Burk plot to answer the following questions:(A)What are the apparent KMand Vmaxvalues in the presence and absence of the inhibitor?(B)What kind of inhibitor is threo-sphingosine? Explain this type of inhibition.
Chapter 24 Solutions
Biochemistry
Ch. 24 - Explaining the Stoichiometry of Fatty Acid...Ch. 24 - Tracing Carbon Atom Incorporation in Fatty Acids...Ch. 24 - Modeling the Regulation of AcetyI-CoA Carboxylase...Ch. 24 - Prob. 4PCh. 24 - Prob. 5PCh. 24 - Prob. 6PCh. 24 - Understanding the Stoichiometry of Cholesterol...Ch. 24 - Prob. 8PCh. 24 - Prob. 9PCh. 24 - Prob. 10P
Ch. 24 - Prob. 11PCh. 24 - Understanding the Mechanism of the...Ch. 24 - Prob. 13PCh. 24 - Understanding the Mechanism of the HMC-CoA...Ch. 24 - Prob. 15PCh. 24 - Prob. 16PCh. 24 - Prob. 17PCh. 24 - Prob. 18PCh. 24 - Prob. 19PCh. 24 - Prob. 20PCh. 24 - Prob. 21PCh. 24 - Prob. 22PCh. 24 - Prob. 23PCh. 24 - Prob. 24PCh. 24 - Prob. 25P
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