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
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
The transformation of compound 2 to vitamin K1 base is exothermic because of
1. The formation of an epoxide.
2. The resulting geminal diol anion.
3. The weak O-O bond.
4. All of the above.
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,.
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
Definition Definition Chemical compound containing two hydroxyl ( - OH ) groups. When naming such compounds, the suffix -diol is added to the name of parent chain alkane.
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