Brain aspartate metabolism

This list is not intended to be comprehensive but to indicate the wide array of neuronal proteins regulated by phosphorylation. Some of the proteins are specific to neurons but most are present in many cell types in addition to neurons and are included because their multiple functions in the nervous system include the regulation of neuron-specific phenomena. Not included are the many phosphoproteins present in diverse tissues, including brain, that play a role in generalized cellular processes, such as intermediary metabolism, and that do not appear to play a role in neuron-specific phenomena. NMDA, N-methyl-D-aspartate CREB, cAMP response element-binding proteins STAT, signal-transducing activators of transcription ... 

THE MALATE-ASPARTATE SHUTTLE HAS A KEY ROLE IN BRAIN METABOLISM 541... 

The malate-aspartate shuttle has a role in linking metabolic pathways in brain 542... 

Berl, S., Nicklas, W. J. and Clarke, D. D. Compartmentation of citric acid cycle metabolism in brain labelling of glutamate, glutamine, aspartate and gaba by several radioactive tracer metabolites. J. Neurochem. 17 1009-1015, 1970. 

Aspartame, N-a-L-aspartyl-L-phenylalanine methyl ester, trade names NutraSweet , and Aspartil , is a dipeptide derivative. Like dipeptides aspartame is metabolised into the constituents, i.e. amino acids and methanol. Therefore studies into the metabolic behaviour and the fate of metabolites were carried out. Levels of blood aspartate and glutamate were measured after intake of high aspartame doses. Changes were transient and allegations of influences of high aspartame levels on brain function could never be verified. 

The biochemical roles of these processes The metabolism of glutamate and aspartate by the enterocytes provides not only ATP, via oxidation of the oxoacids, but can also be considered to be a detoxification process. Both glutamate and aspartate are neurotransmitters in the brain. If their concentrations in blood increase too much, they could interfere with the control of neurotransmitter levels in the brain with possible changes in behaviour or clinical problems (see below). One such phenomenon is Chinese Restaurant Syndrome , but there may be other problems, as yet not reparted. 

Transaminases participate in metabolism of most of the amino acids, over 60 different enzymes have been identified.142163 Best studied are the aspartate aminotransferases, a pair of cytosolic and mitochondrial isoenzymes which can be isolated readily from animal hearts. Their presence in heart muscle and brain in high concentration is thought to be a result of their functioning in the malate-aspartate shuttle... 

This transfer of reducing equivalents is essential for maintaining the favorable NAD+/NADH ratio required for the oxidative metabolism of glucose and synthesis of glutamate in brain (McKenna et al., 2006). The malate-aspartate shuttle is considered the most important shuttle in brain. It is particularly important in neurons. It has low activity in astrocytes. This shuttle system is fully reversible and linked to amino acid metabolism with the energy charge and citric acid cycle of neuronal cells. 

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