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In the presence of potassium cation, O, and CO, the enzyme microsomal carboxylase will convert glufamate side chains of prothrombin (an essential protein for blood clotting) to y-carboxyglutamate groups. This is formally the addition of a CO, group, which is the reverse of a decarboxylation as is common for B-dicarboxylic acids such as malonic acid. The resulting two carboxylates of the chemically modified glutamate now form a tight bidentate ("two teeth") complex with Ca+ during the blood- clotting process. If prothrombin is not carboxylated, it does not bind calcium, and blood does not clot. For decades the role of vitamin K, and 0,in this process Vitamin K deficiency results in slowed blood clotting, which can be a serious threat to a wounded animal or human. In the process of blood clotting, the natural vitamin, which is a quinone, is converted to its active hydroquinone form by reduction. OH .R R tworclectron reduction Vitamin K, quinone Vitamin K, hydroquinone was unknown. pK CH,-CH -CH,-CH vit. K COO COO Glutamate side chain of prothrombin COO Ca+ CH -CH-CH Ca2+ COO Carboxylated glutamate side chain Carboxylated glutamate side chain binding calcium ion Paul Dowd, from the University of Pittsburgh, discovered that the vitamin K, hydroquinone anion reacts with oxygen (0,) to give the peroxide anion intermediate 1, which is converted to compound 2, and then to what is referred to as "vitamin K, base." This species deprotonates a glutamate side chain leading to carboxylation via reaction with CO,. .R HO HO HO 0: :0-0: Vitamin K, hydroquinone anion (a weak base) Vitamin K, base (a very strong base) 1

In the presence of potassium cation, O, and CO, the enzyme microsomal carboxylase will convert glufamate side chains of prothrombin (an essential protein for blood clotting) to y-carboxyglutamate groups. This is formally the addition of a CO, group, which is the reverse of a decarboxylation as is common for B-dicarboxylic acids such as malonic acid. The resulting two carboxylates of the chemically modified glutamate now form a tight bidentate ("two teeth") complex with Ca+ during the blood- clotting process. If prothrombin is not carboxylated, it does not bind calcium, and blood does not clot. For decades the role of vitamin K, and 0,in this process Vitamin K deficiency results in slowed blood clotting, which can be a serious threat to a wounded animal or human. In the process of blood clotting, the natural vitamin, which is a quinone, is converted to its active hydroquinone form by reduction. OH .R R tworclectron reduction Vitamin K, quinone Vitamin K, hydroquinone was unknown. pK CH,-CH -CH,-CH vit. K COO COO Glutamate side chain of prothrombin COO Ca+ CH -CH-CH Ca2+ COO Carboxylated glutamate side chain Carboxylated glutamate side chain binding calcium ion Paul Dowd, from the University of Pittsburgh, discovered that the vitamin K, hydroquinone anion reacts with oxygen (0,) to give the peroxide anion intermediate 1, which is converted to compound 2, and then to what is referred to as "vitamin K, base." This species deprotonates a glutamate side chain leading to carboxylation via reaction with CO,. .R HO HO HO 0: :0-0: Vitamin K, hydroquinone anion (a weak base) Vitamin K, base (a very strong base) 1

Chemistry
Chemistry
10th Edition
ISBN:9781305957404
Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Chapter1: Chemical Foundations
Section: Chapter Questions
Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...
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Which of the following is a challenge to understanding how the carboxylation of glutamate side chains is feasible in a biological setting?

1. Because the pKa of the a-hydrogen of glutamate is 27, it is too high to be effectively deprotonated at physiological pH.

2. The C-C bond formed in a 1,3-dicarboxylate is too weak to exist in a biological setting.

3. b-Dicarboxylic acids spontaneously decarboxylate at neutral pH.

4. Both 1 and 3.

In the presence of potassium cation, O, and CO, the enzyme microsomal carboxylase will convert glufamate side chains of prothrombin (an essential protein for blood clotting) to y-carboxyglutamate groups. This is formally the addition of a CO, group, which is the reverse of a decarboxylation as is common for B-dicarboxylic acids such as malonic acid. The resulting two carboxylates of the chemically modified glutamate now form a tight bidentate ("two teeth") complex with Ca+ during the blood- clotting process. If prothrombin is not carboxylated, it does not bind calcium, and blood does not clot. For decades the role of vitamin K, and 0,in this process Vitamin K deficiency results in slowed blood clotting, which can be a serious threat to a wounded animal or human. In the process of blood clotting, the natural vitamin, which is a quinone, is converted to its active hydroquinone form by reduction. OH .R R tworclectron reduction Vitamin K, quinone Vitamin K, hydroquinone was unknown. pK CH,-CH -CH,-CH vit. K COO COO Glutamate side chain of prothrombin COO Ca+ CH -CH-CH Ca2+ COO Carboxylated glutamate side chain Carboxylated glutamate side chain binding calcium ion Paul Dowd, from the University of Pittsburgh, discovered that the vitamin K, hydroquinone anion reacts with oxygen (0,) to give the peroxide anion intermediate 1, which is converted to compound 2, and then to what is referred to as "vitamin K, base." This species deprotonates a glutamate side chain leading to carboxylation via reaction with CO,.
Transcribed Image Text:In the presence of potassium cation, O, and CO, the enzyme microsomal carboxylase will convert glufamate side chains of prothrombin (an essential protein for blood clotting) to y-carboxyglutamate groups. This is formally the addition of a CO, group, which is the reverse of a decarboxylation as is common for B-dicarboxylic acids such as malonic acid. The resulting two carboxylates of the chemically modified glutamate now form a tight bidentate ("two teeth") complex with Ca+ during the blood- clotting process. If prothrombin is not carboxylated, it does not bind calcium, and blood does not clot. For decades the role of vitamin K, and 0,in this process Vitamin K deficiency results in slowed blood clotting, which can be a serious threat to a wounded animal or human. In the process of blood clotting, the natural vitamin, which is a quinone, is converted to its active hydroquinone form by reduction. OH .R R tworclectron reduction Vitamin K, quinone Vitamin K, hydroquinone was unknown. pK CH,-CH -CH,-CH vit. K COO COO Glutamate side chain of prothrombin COO Ca+ CH -CH-CH Ca2+ COO Carboxylated glutamate side chain Carboxylated glutamate side chain binding calcium ion Paul Dowd, from the University of Pittsburgh, discovered that the vitamin K, hydroquinone anion reacts with oxygen (0,) to give the peroxide anion intermediate 1, which is converted to compound 2, and then to what is referred to as "vitamin K, base." This species deprotonates a glutamate side chain leading to carboxylation via reaction with CO,.
.R HO HO HO 0: :0-0: Vitamin K, hydroquinone anion (a weak base) Vitamin K, base (a very strong base) 1
Transcribed Image Text:.R HO HO HO 0: :0-0: Vitamin K, hydroquinone anion (a weak base) Vitamin K, base (a very strong base) 1
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