ALT catalyzes the reaction between L-alanine and 2-oxoglutarate. The pyruvate formed is reduced by NADH in a reaction catalyzed by lactate dehydrogenase (LDH) to form L-lactate and NAD+. Pyridoxal phosphate serves as a coenzyme in the amino transfer reaction. It ensures full enzyme activation.
L-alanine + α-ketoglutarate > ALT > pyruvate + L-glutamate
Pyruvate + NADH + H+ > LDH > L-lactate + NAD+