File:Malate-aspartate_shuttle_(zh-cn).svg licensed with Cc-by-sa-3.This image is a derivative work of the following images: By utilizing the glutamate: oxaloacetate aminotransferase and malate dehydrogenase present in glyoxysomes and mitochondria, reducing equivalents could be transferred between the organelles by a malate-aspartate shuttle. CC BY-SA 3.0 Creative Commons Attribution-Share Alike 3.0 true true Original upload log Glyoxysomes isolated from germinating castor bean endosperm accumulate NADH by -oxidation of fatty acids. share alike – If you remix, transform, or build upon the material, you must distribute your contributions under the same or compatible license as the original.You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use. attribution – You must give appropriate credit, provide a link to the license, and indicate if changes were made.to share – to copy, distribute and transmit the work.This reaction takes place on the inner mitochondrial membrane, allowing FADH2 to donate its electrons directly to coenzyme Q (ubiquinone) which is part of the electron transport chain which ultimately transfers electrons to molecular oxygen O2, with the formation of water, and the release of energy eventually captured in the form of ATP. malate-aspartate shuttle and citric acid cycle in rat hear mitochondria. Glycerol-3-phosphate is then reoxidized to dihydroxyacetone, donating its electrons to FAD instead of NAD+. OXIDATION OF CYTOSOLIC NADH BY THE MALATE-ASPARTATE. In the glycerol phosphate shuttle electrons from cytosolic NADH are transferred to dihydroxyacetone to form glycerol-3-phosphate which readily traverses the outer mitochondrial membrane. though several indirect shuttle mechanisms have been proposed (5-7), current evidence indicates that the reducing equivalents formed in the re- duction of cytosolic NAD to NADH are indirectly carried into the mitochondrial compartment of the heart and other tissues by metabolic anions of the malate-aspartate cycle (8-11). The oxaloacetate is then re-cycled to the cytosol via its conversion to aspartate which is readily transported out of the mitochondrion. The results suggest that Ca2+-regulated Aralar-MAS activation upregulates glycolysis and pyruvate production, which fuels mitochondrial respiration, through regulation of cytosolic NAD+/NADH ratio. The malate then traverses the inner mitochondrial membrane into the mitochondrial matrix, where it is reoxidized by NAD+ forming intra-mitochondrial oxaloacetate and NADH. However, Ca2+ stimulation is blunt in the absence of Aralar, a Ca2+-binding mitochondrial carrier component of Malate-Aspartate Shuttle (MAS). In the former the electrons from NADH are transferred to cytosolic oxaloacetate to form malate. Because transport of NADH into mitochondria by the malate-aspartate shuttle requires a stoichiometric influx of malate and glutamate and efflux of aspartate. The malate-aspartate (M-A) shuttle provides an important mechanism to regulate glycolysis and lactate metabolism in the heart by transferring reducing equivalents from cytosol into mitochondria. They are the malate-aspartate shuttle and the glycerol phosphate shuttle. Use is therefore made of two “shuttles” to transport the electrons from NADH across the mitochondrial membrane. However the inner mitochondrial membrane is impermeable to NADH and NAD+. The malate-aspartate shuttle (sometimes simply the malate shuttle) is a biochemical system for translocating electrons produced during glycolysis across the semipermeable inner membrane of the mitochondrion for oxidative phosphorylation in eukaryotes. Firstly, the NADH + H+ generated by glycolysis has to be transferred to the mitochondrion to be oxidized, and thus to regenerate the NAD+ necessary for glycolysis to continue.
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