title: Identification, expression and bioactivity of hexokinase in amphioxus: insights into evolution of vertebrate hexokinase genes.
abstract: Hexokinase family includes hexokinases I, II, III and IV, that catalyze the phosphorylation of glucose to produce glucose 6-phosphate. Hexokinase IV, also known as glucokinase, is only half size of the other types of hexokinases that contain two hexokinase domains. Despite the enormous progress in the study of hexokinases, the evolutionary relationship between glucokinase and other hexokinases is still uncertain, and the molecular processes leading to the emergence of hexokinases in vertebrates remain controversial. Here we clearly demonstrated the presence of a single hexokinase-like gene in the amphioxus Branchiostoma japonicum, Bjhk, which shows a tissue-specific expression pattern, with the most abundant expression in the hepatic caecum, testis and ovary. The phylogenetic and synteny analyses both reveal that BjHK is the archetype of vertebrate hexokinases IV, i.e. glucokinases. We also found for the first time that recombinant BjHK showed functional enzyme activity resembling vertebrate hexokinases I, II, III and IV. In addition, a native glucokinase activity was detected in the hepatic caecum. Finally, glucokinase activity in the hepatic caecum was markedly reduced by fasting, whereas it was considerably increased by feeding. Altogether, these suggest that Bjhk represents the archetype of glucokinases, from which vertebrate hexokinase gene family was evolved by gene duplication, and that the hepatic caecum plays a role in the control of glucose homeostasis in amphioxus, in favor of the notion that the hepatic caecum is a tissue homologous to liver.
authors.affiliation: Laboratory for Evolution & Development, Institute of Evolution & Marine Biodiversity and Department of Marine Biology, Ocean University of China, Qingdao 266003, China.
authors.forename: Mengyang
authors.initials: M
authors.lastname: Li
authors.affiliation: Laboratory for Evolution & Development, Institute of Evolution & Marine Biodiversity and Department of Marine Biology, Ocean University of China, Qingdao 266003, China.
authors.forename: Zhan
authors.initials: Z
authors.lastname: Gao
authors.affiliation: Laboratory for Evolution & Development, Institute of Evolution & Marine Biodiversity and Department of Marine Biology, Ocean University of China, Qingdao 266003, China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Wang
authors.affiliation: Laboratory for Evolution & Development, Institute of Evolution & Marine Biodiversity and Department of Marine Biology, Ocean University of China, Qingdao 266003, China. Electronic address: sczhang@ouc.edu.cn.
authors.forename: Shicui
authors.initials: S
authors.lastname: Zhang
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D004789:Enzyme Activation; D015870:Gene Expression; D020869:Gene Expression Profiling; D023061:Gene Order; D005947:Glucose / Q000378:metabolism; D006593:Hexokinase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D006706:Homeostasis; D006801:Humans; D007527:Isoenzymes; D064175:Lancelets / Q000145:classification / Q000201:enzymology* / Q000235:genetics*; D008954:Models, Biological; D008958:Models, Molecular; D008969:Molecular Sequence Data; D005810:Multigene Family; D009928:Organ Specificity / Q000235:genetics; D010802:Phylogeny; D011487:Protein Conformation; D014714:Vertebrates
chemical_list: D007527:Isoenzymes; D006593:Hexokinase; D005947:Glucose
keywords: 4(2hydroxyethyl)-1-piperazine ethanesulfonic acid; ATP; Amphioxus; Bp; DAB; DNA; DTT; G6PDH; GCK; Glucokinase; Glucose homeostasis; HEPES; HK; HRP; Hepatic caecum; Hexokinase; IPTG; KDa; LB; M; NADP; ORF; PAGE; PBS; PCR; RACE; RNA; SD; SDS; TBS; Tris; UTR; adenosine triphosphate; base pair; deoxyribonucleic acid; diaminobenzidine; dithiothreitol; glucokinase; glucose-6-phosphate dehydrogenase; h; hexokinase; horseradish peroxidase; hour; isoelectric point; isopropyld-thiogalactoside; kilodalton; lysogeny broth; min; minute; mole per liter; nicotinamide-adenine dinucleotide phosphate; open reading frame; pH; pI; phosphate-buffered saline; polyacrylamide gel electrophoresis; polymerase chain reaction; potential of hydrogen; qRT-PCR; quantitative real-time PCR; rapid-amplification of cDNA ends; ribonucleic acid; s; second; sodium dodecyl sulfate; standard deviation; tris (hydroxymethyl) aminomethane; tris (hydroxymethyl) aminomethane-buffered saline; untranslated region