Kinetics of peptide hydrolysis and amino acid decomposition at high temperature

Testing the limitations of artificial protein degradation kinetics using known-age massive Porites coral skeletons

“…These estimates are higher than activation energies calculated under ideal conditions (dipeptides heated in the laboratory; E a 83-99 kJ mol −1 e.g. Kriausakul and Mitterer, 1980 ;Qian et al, 1993) probably due to the effect of protein structure on the hydrolysis rates: estimated E a 's are elevated because they also include rate changes associated with protein denaturation, hydrolysis being faster in disordered peptide chains. An additional factor will be the rate of decomposition of free amino acids.…”

“…As the %FAA actually represents the liberation of FAA (hydrolysis) minus FAA lost by decomposition, if decomposition and hydrolysis reactions have significantly different temperature dependence, then this limits the use of %FAA as a proxy for hydrolysis when extrapolating from high temperature experiments. For example, the deamination of free aspartic acid in buffered solution (E a 154 kJ mol −1 at pH 7; Bada and Miller, 1970) has a greater temperature sensitivity than hydrolysis of the Gly-Gly peptide bond in dipeptides (∼44 kJ mol −1 at 265 atm or ∼99 kJ mol −1 at water steam pressure; Qian et al, 1993). If hydrolysis of peptide bonds involving Asx has a similar temperature sensitivity to the Gly dipeptide, accelerated high-temperature decomposition of Asp would lower the %FAA and underestimate the rate of hydrolysis.…”

Effects of metal ions and pH on the formation and decomposition rates of di- and tri-peptides in aqueous solution

“…To estimate the reaction rates, we considered the following reactions, where k n is the reaction rate constant (Fig. 4): 1) formation of GlyGly from Gly (second-order reaction, k 1 ), 2) formation of DKP from GlyGly (first-order reaction, k 2 ), 3) hydrolysis of GlyGly to produce Gly (first-order reaction, k -1 ), 4) hydrolysis of DKP to produce GlyGly (first-order reaction, k -2 ) (Qian et al, 1993;Li and Brill, 2003), 5) formation of GlyGlyGly from Gly and GlyGly (second-order reaction, k 3 ), and 6) hydrolysis of GlyGlyGly to produce Gly and GlyGly (first-order reaction, k -3 ).…”

Development of Micro-Flow Hydrothermal Monitoring Systems and Their Applications to the Origin of Life Study on Earth

“…39 The association constants became too small be measured at temperatures of over 125 C. It was confirmed that the logarithmic values of the association constants for different sizes of hetercyclic bases are proportional to the number of rings of the heterocyclic bases at temperatures of 25 -100 C; these phenomena were previously discovered using a conventional absorption spectrophotometer at 25 C, where the association is basically due to the π-π stacking interaction. 40 Thus, the fact that the association constants are proportional to the ring number at higher temperatures of over 25 C reflects that the association is due to π-π stacking. In addition, a decrease of the association with an increase of temperature reflects the decrease of π-π stacking with an increase of temperature.…”

“…23,40 The degradation and behavior of nucleotides, RNA, amino acids, peptides at high temperatures were investigated on the basis of the experimental data, which were determined at relatively low temperatures within a few minutes to a few hours. [40][41][42][43][44][45] Thus, the details concerning the stability and behavior of these biomolcules could not be evaluated properly unless using real-time and in situ monitoring techniques. The hydrothermal flow reactor systems for real-time and in situ monitoring allowed us to investigate several reaction behaviors regarding the chemical evolution of RNA and peptides under the simulated primitive earth conditions.…”