Role of Lysine in catalysing Ester Hydrolysis
RECENTLY, Gero and Withrow1 have cited the catalysis of alkaline triglyceride hydrolysis by lysine as a chemical model of a biological reaction. They postulated a bifunctional2 attack by lysine upon the carbonyl O and C of the ester linkage as the mechanism of this hydrolysis.
Kinetics of aldose-amino acid interaction.
Abstract 1. 1. The kinetics of the reaction between various aldoses and amino acids and peptides has been investigated. 2. 2. A method for the determination of rate constants, based on the addition of alkali to keep the pH of the reaction mixture constant, has been developed. 3. 3. The velocity of the reaction decreases with increase of pH according to the equation dRG − d t = R − .G kα + kβ .OH − − RG − (kα + kβ .OH − )L where RG − is the concentration of the reaction product, R − —that of the amino acid anion, G—of the aldose; OH − —the hydroxyl ion concentration and k α , k β pH independent rate constants. 4. 4. The rate constant k β is inversely proportional to the rate constant of the primary attack of the amino acid on the aldose. The rate of the primary reaction increases with the basicity of the amino component in accordance with the Hammett relation.
Enzyme-Substrate Complexes.
A computational method for estimating the relative binding free nergies of enzyme-substrate complexes is described that combines electrostatic and solvation models and X-ray crystallographic data. The polar contribution is evaluated by the Poisson-Boltzman equation. The nonpolar contribution is evaluated by solvent transfer data and surface area calculations. This algorithm was used to calculate the relative binding energies of 63 pairs of nine different mutant proteins with seven different substituted R-malate substrates of Escherichia coli isocitrate dehydrogenase. Comparison of calculated values with the experimentally observed values shows a high degree of correlation.