Basis for the equilibrium constant in the interconversion of l-lysine and l-beta-lysine by lysine 2,3-aminomutase. Biochim Biophys Acta 2007 Feb;1774(2):297-302
Date
01/27/2007Pubmed ID
17254853Pubmed Central ID
PMC2045507DOI
10.1016/j.bbapap.2006.12.002Scopus ID
2-s2.0-33846829327 (requires institutional sign-in at Scopus site) 10 CitationsAbstract
l-beta-lysine and beta-glutamate are produced by the actions of lysine 2,3-aminomutase and glutamate 2,3-aminomutase, respectively. The pK(a) values have been titrimetrically measured and are for l-beta-lysine: pK(1)=3.25 (carboxyl), pK(2)=9.30 (beta-aminium), and pK(3)=10.5 (epsilon-aminium). For beta-glutamate the values are pK(1)=3.13 (carboxyl), pK(2)=3.73 (carboxyl), and pK(3)=10.1 (beta-aminium). The equilibrium constants for reactions of 2,3-aminomutases favor the beta-isomers. The pH and temperature dependencies of K(eq) have been measured for the reaction of lysine 2,3-aminomutase to determine the basis for preferential formation of beta-lysine. The value of K(eq) (8.5 at 37 degrees C) is independent of pH between pH 6 and pH 11; ruling out differences in pK-values as the basis for the equilibrium constant. The K(eq)-value is temperature-dependent and ranges from 10.9 at 4 degrees C to 6.8 at 65 degrees C. The linear van't Hoff plot shows the reaction to be enthalpy-driven, with DeltaH degrees =-1.4 kcal mol(-1) and DeltaS degrees =-0.25 cal deg(-1) mol(-1). Exothermicity is attributed to the greater strength of the bond C(beta)-N(beta) in l-beta-lysine than C(alpha)-N(alpha) in l-lysine, and this should hold for other amino acids.
Author List
Chen D, Tanem J, Frey PAAuthor
Justinn M. Tanem MD Assistant Professor in the Anesthesiology department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
Glutamic AcidHydrogen-Ion Concentration
Intramolecular Transferases
Ions
Kinetics
Lysine
Stereoisomerism