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Oxaloacetate + 2 H + + 2 e − → Malate-0.17 [10] While under standard conditions malate cannot reduce the more electronegative NAD +:NADH couple, in the cell the concentration of oxaloacetate is kept low enough that Malate dehydrogenase can reduce NAD + to NADH during the citric acid cycle. Fumarate + 2 H + + 2 e − → Succinate +0.03 [9]
Malate is acted on by malate dehydrogenase to become oxaloacetate, producing a molecule of NADH. After that, oxaloacetate will be recycled to aspartate, as transaminases prefer these keto acids over the others. This recycling maintains the flow of nitrogen into the cell. Relationship of oxaloacetic acid, malic acid, and aspartic acid
In enzymology, a malate oxidase (EC 1.1.3.3) is an enzyme that catalyzes the chemical reaction (S)-malate + O 2 oxaloacetate + H 2 O 2. Thus, the two substrates of this enzyme are (S)-malate and O 2, whereas its two products are oxaloacetate and H 2 O 2.
Malate, in the mitochondrial matrix, can be used to make pyruvate (catalyzed by malic enzyme) or oxaloacetic acid, both of which can enter the citric acid cycle. Glutamine can also be used to produce oxaloacetate during anaplerotic reactions in various cell types through "glutaminolysis", which is also seen in many c-Myc transformed cells. [ 3 ]
The amino acid sequences of archaeal MDH are more similar to that of LDH than that of MDH of other organisms. This indicates that there is a possible evolutionary linkage between lactate dehydrogenase and malate dehydrogenase. [8] Each subunit of the malate dehydrogenase dimer has two distinct domains that vary in structure and functionality.
Malate is oxidized to pyruvate and CO 2, and NADP + is reduced to NADPH. This enzyme belongs to the family of oxidoreductases, to be specific those acting on the CH-OH group of donor with NAD + or NADP + as acceptor. The systematic name of this enzyme class is (S)-malate:NADP + oxidoreductase (oxaloacetate-decarboxylating).
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.
The reaction it catalyzes is: pyruvate + HCO − 3 + ATP → oxaloacetate + ADP + P. It is an important anaplerotic reaction that creates oxaloacetate from pyruvate. PC contains a biotin prosthetic group [1] and is typically localized to the mitochondria in eukaryotes with exceptions to some fungal species such as Aspergillus nidulans which have a cytosolic PC.