Glutaminase

Overview
Glutaminase is a amidohydrolase enzyme which generates glutamate from glutamine. Glutaminase has tissue-specific isoenzymes.

Glutaminase catalyzes the following reaction:

Glutamine + H2O → Glutamate + NH3

Glutaminase is expressed in periportal hepatocytes, where it generates NH3 (ammonia) for urea synthesis.

Glutaminase is also expressed in the epithelial cells of the renal tubules, where the produced ammonia is excreted as ammonium ions. This excretion of ammonium ions is an important mechanism of renal acid-base regulation. During an acidosis, glutaminase is induced in the kidney, which leads to an increase in the amount of ammonium ions excreted.