Transamination is the process of transferring anime groups from amino acids. This is used with glutamate, allowing the transfer of -NH2 groups to other molecules. As glutamate is a carrier molecule for -NH2, this is beneficial as it allows the transfer of nitrogen groups - given it is not possible to fix atmospheric nitrogen, it must be kept on carrier molecules to prevent loss.
After transamination, the glutamate becomes an alpha-ketoglutarate.