Aspartaat

Aspartaat, or aspartate, is the deprotonated form of aspartic acid that predominates in physiological conditions. It is one of the nonessential amino acids and exists mainly in the L-enantiomer form within proteins. In solution, aspartate carries a negative charge at neutral pH and participates in various metabolic pathways as an amino group donor or acceptor.

In metabolism, aspartate plays a central role in transamination reactions. It is formed by the transfer of an amino group from glutamate to oxaloacetate via the enzyme aspartate aminotransferase, generating aspartate and α-ketoglutarate. Aspartate provides amino groups for the synthesis of pyrimidine and purine nucleotides, and it serves as a substrate in the urea cycle for the formation of argininosuccinate. It also participates in the malate-aspartate shuttle, aiding the transport of reducing equivalents into mitochondria. In the nervous system, aspartate functions as an excitatory neurotransmitter alongside glutamate.

Biologically, free aspartate is present in tissues and fluids, and its levels are monitored in clinical contexts. The enzyme aspartate aminotransferase (AST) catalyzes the reversible transamination between aspartate and α-ketoglutarate. Elevated AST activity in serum can indicate liver or muscle injury, and is commonly measured alongside alanine aminotransferase (ALT) in liver function tests.

In nutrition, aspartate is found in most protein-containing foods and is produced endogenously. It is not considered an essential amino acid for humans, but it participates in many biosynthetic pathways and energy metabolism.