title: Degradation kinetics of L-alanyl-L-glutamine and its derivatives in aqueous solution.
abstract: The degradation kinetics of five glutamine dipeptides in aqueous solution, i.e. glycyl-L-glutamine (Gly-Gln), L-alanyl-L-glutamine (Ala-Gln), L-valyl-L-glutamine (Val-Gln), L-leucyl-L-glutamine (Leu-Gln) and L-isoleucyl-L-glutamine (Ile-Gln), were studied. Stability tests were performed using a stability-indicating high-performance liquid chromatographic assay. Two different Ala-Gln degradation routes, i.e. the cleavage of a peptide bond and the deamination of an amide group, were observed. The degradation was adequately described by pseudo-first-order kinetics. The maximum stability of Ala-Gln was obtained at an approximate pH of 6.0. The pH-rate profile described by specific acid-base catalysis and hydrolysis by water molecules agreed with the experimental results. The activation energy of Ala-Gln at pH 6.0 was determined to be 27. 1kcal mol-1, and the shelf-life (90% remaining) at 25 and 40 degrees C was predicted to be 5.3 years and 7.1 months, respectively. The rate constants of the glutamine dipeptides were influenced by the N-terminal amino acid residue and decreased in the order: Gly-Gln, Ala-Gln, Leu-Gln, Val-Gln and Ile-Gln.
authors.affiliation: Preclinical Development Laboratories, Hoechst Marion Roussel Ltd., 1658 Ohshinohara, Yasu-cho, Yasu-gun, Shiga 520-23, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Arii
authors.forename: T
authors.initials: T
authors.lastname: Kai
authors.forename: Y
authors.initials: Y
authors.lastname: Kokuba
mesh_terms: D004151:Dipeptides / Q000737:chemistry*; D004355:Drug Stability; D006863:Hydrogen-Ion Concentration; D012996:Solutions; D013696:Temperature
chemical_list: D004151:Dipeptides; D012996:Solutions; C045560:alanylglutamic acid