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The reaction is similar to the reaction catalysed by pyruvate kinase, which also converts pyruvate to PEP. [3] However, pyruvate kinase catalyses an irreversible reaction, and does not consume ATP. By contrast, PPDK catalyses a reversible reaction, and consumes 1 molecule of ATP for each molecule of pyruvate converted.
1. CO 2 is fixed to produce a four-carbon molecule (malate or aspartate). 2. The molecule exits the cell and enters the bundle sheath cells. 3. It is then broken down into CO 2 and pyruvate. CO 2 enters the Calvin cycle to produce carbohydrates. 4. Pyruvate reenters the mesophyll cell, where it is reused to produce malate or aspartate.
One molecule of glucose breaks down into two molecules of pyruvate, [10] which are then used to provide further energy, in one of two ways. Pyruvate is converted into acetyl-coenzyme A , which is the main input for a series of reactions known as the Krebs cycle (also known as the citric acid cycle or tricarboxylic acid cycle).
Pyruvate is oxidized to acetyl-CoA and CO 2 by the pyruvate dehydrogenase complex (PDC). The PDC contains multiple copies of three enzymes and is located in the mitochondria of eukaryotic cells and in the cytosol of prokaryotes. In the conversion of pyruvate to acetyl-CoA, one molecule of NADH and one molecule of CO 2 is formed. [11]
The pyruvate produced by glycolysis is an important intermediary in the conversion of carbohydrates into fatty acids and cholesterol. [46] This occurs via the conversion of pyruvate into acetyl-CoA in the mitochondrion. However, this acetyl CoA needs to be transported into cytosol where the synthesis of fatty acids and cholesterol occurs.
1) Carbon is fixed to produce oxaloacetate by PEP carboxylase. 2) The four carbon molecule then exits the cell and enters the chloroplasts of bundle sheath cells. 3) It is then broken down releasing carbon dioxide and producing pyruvate. Carbon dioxide combines with ribulose bisphosphate and proceeds to the Calvin Cycle.
Pyruvate oxidation is the step that connects glycolysis and the Krebs cycle. [4] In glycolysis, a single glucose molecule (6 carbons) is split into 2 pyruvates (3 carbons each). Because of this, the link reaction occurs twice for each glucose molecule to produce a total of 2 acetyl-CoA molecules, which can then enter the Krebs cycle.
The by-product pyruvate can be further degraded in the mitochondrial citric acid cycle, thereby providing additional CO 2 molecules for the Calvin Cycle. Pyruvate can also be used to recover PEP via pyruvate phosphate dikinase, a high-energy step, which requires ATP and an additional phosphate. During the following cool night, PEP is finally ...