Glucose-6-phosphatase is a multicomponent enzyme composed of a transporter subunit and a catalytic subunit that is involved in hepatic glucose production. The objective of the present study was to determine the complete nucleotide sequence of feline hepatic glucose-6-phosphatase catalytic subunit (G6Pc) cDNA and to perform comparative analysis of the molecular features of the feline G6Pc cDNA and protein. Feline G6Pc cDNA contains 2261 bases and encodes a 357 aa protein. The feline cDNA and protein are highly conserved with overall identity ranging from 73-86% to 86-95%, respectively, among mammalian species. Membrane topology, phosphatase consensus sequence, ER retention sequence, N-glycosylation sites and active site residues are conserved in the feline protein. Analysis of the putative feline G6Pc protein did not reveal any species-specific features to explain the unusual in vivo regulation of G6Pase activity reported in feline liver.

BackgroundGlucokinase (GK) is a metabolic enzyme encoded by the GCK gene and expressed in glucose-sensitive tissues, principally pancreatic islets cell and hepatocytes. The GK protein acts in pancreatic islets as a “glucose sensor” that couples fluctuations in the blood glucose concentration to changes in cellular function and insulin secretion. GCK and GK have proposed importance in the development and progression of diabetes mellitus and are potential therapeutic targets for diabetes treatment. The study was undertaken to determine the nucleotide sequence of feline pancreatic GK cDNA, predict the amino acid sequence and structure of the feline GK protein, and perform comparative bioinformatic analysis of feline cDNA and protein. Routine PCR techniques were used with cDNA from feline pancreas. Clones were assembled to obtain the full length cDNA. Protein prediction and modeling were performed using bioinformatic tools.ResultsFull-length feline pancreatic GK cDNA contains a 1398 nucleotide coding sequence with high identity to other pancreatic GK cDNAs. The deduced 465 amino acid feline protein has 15 amino acid substitutions not found in other mammalian GK proteins but maintains high structural homology with human GK. Feline pancreatic GK is highly conserved at nucleotide and protein levels. Residues crucial for substrate binding and catalysis are completely conserved in the feline protein.ConclusionMolecular analysis predicts that feline pancreatic GK functions similarly to other mammalian GK proteins.