L-Glutamine is transported into the cytoplasm through a glutamine ABC transporter. Once inside, L-glutamine is metabolized with glutaminase to produce an L-glutamic acid. This process can be reversed through a glutamine synthetase resulting in L-glutamine. L-glutamic acid can also be transported into the cytoplasm through various methods: a glutamate/aspartate:H+ symporter GltP, a glutamate:sodium symporter, or a glutamate/aspartate ABC transporter. L-Glutamic acid can proceed to L-glutamate metabolism or it can undergo a reversible reaction through a glutamate racemase resulting in D-glutamic acid. This compound can also be obtained from D-glutamine interacting with a glutaminase. D-Glutamic acid reacts with UDP-N-acetylmuramoyl-L-alanine through an ATP-driven UDP-N-acetylmuramoylalanine-D-glutamate ligase resulting in a UDP-N-acetylmuramoyl-L-alanyl-D-glutamate which is then integrated into peptidoglycan biosynthesis. UDP-N-acetylmuramoyl-L-alanine comes from the amino sugar and nucleotide sugar metabolism product, UDP-N-acetylmuraminate which reacts with L-alanine through an ATP-driven UDP-N-acetylmuramate-L-alanine ligase.

D-Glutamine and D-Glutamate Metabolism References