Α-Aminoadipic acid

α-Aminoadipic acid is one of the metabolic precursor in the biosynthesis of lysine through α-aminoadipate pathway. Its conjugate base is α-aminoadipate, which is the prevalent form at physiological pH.

α-Aminoadipic acid has a stereogenic center and can appear in two enantiomers, <small>L</small>-α-aminoadipate and <small>D</small>-α-aminoadipate. The <small>L</small>-enantiomer appears during lysine biosynthesis and degradation, whereas the <small>D</small>-enantiomer is a part of certain antibiotics.

Metabolism

Lysine degradation

Through saccharopine and allysine, lysine is converted to α-aminoadipate, which is then degraded all the way to acetoacetate. Allysine is oxidized by aminoadipate-semialdehyde dehydrogenase:

α-Aminoadipate is then transaminated with α-ketoglutaric acid to give 2-oxooadipic acid and L-glutamic acid, respectively, by the action of 2-aminoadipate transaminase:

Lysine biosynthesis

α-Aminoadipate appears during biosynthesis of lysine in several yeast species, fungi, and certain protists. During this pathway, which is named after α-aminoadipate, the same steps are repeated in the opposite order as in the degradation reactions, namely, α-ketoadipate is transaminated to α-aminoadipate, which is then reduced to allysine, allysine couples with glutamate to give saccharopine, which is then cleaved to give lysine.

Importance

A 2013 study identifieds α-aminoadipate as a novel predictor of the development of diabetes and suggested that it is a potential modulator of glucose homeostasis in humans.

<small>D</small>-α-Aminoadipic acid is a part of the antibiotic cephalosporin C.

References