Teleost liver hexokinase- and glucokinase-like enzymes: partial cDNA cloning and phylogenetic studies in rainbow trout (Oncorhynchus mykiss), common carp (Cyprinus carpio) and gilthead seabream (Sparus aurata)

The efficiency of enzymatic conversion of glucose into glucose-6-phosphate in fish fed carbohydrates is still a matter of debate. This study reports t he first ever identification of hexokinase-family members at a molecular le vel in fish. The deduced amino acid sequences of six cDNA clones allowed th eir assignement either to hexokinase IV (glucokinase) for rainbow trout (On corhynchus mykiss), common carp (Cyprinus carpio) and gilthead seabream (Sp arus aurata) or to hexokinase I/II for the common carp (two clones) and the gilthead seabream, based on their similarities to known members of the HK family. The evolutionary relationships among these sequences were investiga ted by phylogenetic analysis. These hexokinase sequences constitute potenti al molecular tools for analysis of interspecific differences in dietary car bohydrate utilization in fish.