Abstract: This invention relates to glutamine:fructose-6-phosphate amidotransferase, or its partial peptide or a salt thereof; a DNA coding for the protein; a recombinant vector; a transformant; a method for producing the protein; a pharmaceutical composition comprising the protein, its partial peptide or a salt thereof; and an antibody against the protein or its partial peptide. The protein, its partial peptide or a salt thereof, and the DNA are useful for a prophylactic or therapeutic agent for hypoglycemia. The antibody can be used in the assay of the protein, its partial peptide or a salt thereof. The protein, its partial peptide or a salt thereof is useful as a reagent for the screening for candidate medical compounds.