Molecular characterization, expression and activity of glucokinase in golden pompano, Trachinotus ovatus: Response of its expression to carbohydrate in the diet

It is well known that the enzyme glucokinase (GK) plays an important role in the control of glucose homeostasis. In the present study, a glucokinase (To-GK) was cloned from golden pompano, Trachinotus ovatus. The To-GK cDNA is composed of 2151 bp with a 33 bp of 5′-UTR, 1437 bp open reading frame (ORF) and 681 bp 3′-UTR, encoding a polypeptide of 478 amino acids (GenBank accession no: ALX36181.1). Phylogenetic analysis revealed that To-GK showed highest similarity to Cynoglossus semilaevis GK. Tissue distribution analysis showed that the highest expression of the To-GK was detected in liver. Then, 8-week feeding trial was conducted to investigate the effects of dietary carbohydrate levels (57.5, 120.4, and 277.7 g kg− 1) on the activity and mRNA expression of To-GK in T. ovatus. Higher GK activity was found in fish fed 277.7 g kg− 1 carbohydrate diet. To-GK expression was higher in fish fed the 277.7 g kg− 1 carbohydrate diet. Overall, our data suggest that the hepatic GK activity and mRNA expression of T. ovatus were up-regulated significantly as dietary carbohydrate levels increased. These results indicated that To-GK plays a crucial role in the adaptation of hepatic glycolysis to dietary high carbohydrates in T. ovatus.