Alanine aminotransferase: A target to improve utilisation of dietary nutrients in aquaculture

Abstract

Alanine aminotransferase (ALT) is a sensitive marker of dietary protein utilisation in fish. Three ALT isoforms (cALT1, cALT2 and mALT) encoded by two genes have been isolated from gilthead sea bream (Sparus aurata). Molecular characterization of ALT isozymes and gene promoters suggest involvement of cALT1 and mALT in postprandial use of dietary amino acids, while cALT2 seems associated to hepatic gluconeogenesis. Inhibition of hepatic cytosolic ALT activity stimulates pyruvate kinase and decreases the renewal rate of alanine in S. aurata. These findings point to ALT as a target to spare protein and improve catabolism of dietary carbohydrates in cultured fish.