Which of the following reactions is highly active in the liver when large amounts of amino acids are moving from extrahepatic tissue to the liver?

A)conversion of glutamate to glutamine
B)oxidation of glutamate by glutamate dehydrogenase
C)reduction of $\alpha$ -ketoglutarate by glutamate dehydrogenase
D)transamination of glutamate and pyruvate to $\alpha$ -ketoglutarate and alanine
E)none of the above