Malate aspartate shuttle, Study notes of Biochemistry

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MALATE ASPARTATE

SHUTTLE

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introuduction

This is a biochemical system for translocating electrons produced during glycolysis across the semi permeable inner membrane of the mitochondrion for oxidative phosphorylation in eukaryotes. These electrons enter the electron transport chain of the mitochondria via reduction equivalents to generate ATP.

COMPONENTS

Consists of 4 proteins: Malate DH in the mitochondrial matrix and intermembrane space Aspartate amino transfarase: in the mitochondrial matrix and intermembrane space. Malate α-KG antiporter in the inner membrane. Glutamate-aspartate antiporter in the inner membrane

MECHANISM

The primary enzyme is Malate DH. It is preasent in two forms: I. mitochondrial malate DH II. Cytosolic MDH. .The two forms are different in there location and structuren and catalyse there reactions in opposite directions in the process. .First in the cytosol MDH catalyses the reaction of oxaloacetate and NADH to produce 2 electrons from NADH and accompanying H+ are attached to OA to form malate.

OA cannot be transported into the cytosol by mitochondrial aspartate aminotransfarase therefore an amino radical must be addded by glutamate hence forming alpha KG by the same enzyme.

The second antiporter imports glutamate from the cytosol into the matrix and exports aspartate from the matrix to the cytosol. Once in the cytosol aspartate is converted by cytosolic aspartate aminotransfarase to oxaloacetate.

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