The mechanism of the oxidative deamination and decarboxylation of serine and threonine by periodate in acid medium

Abstract

ROSA PASCUAL and MIGUEL A. HERRAEZ. Can. J. Chem. 63, 2349 (1985). The kinetics of oxidation of serine and threonine by periodate have been investigated in acid medium at 10°C. The reaction rate is first order in both periodate and amino acid, and the overall reaction follows second-order kinetics. The rates decrease with increase in [H']. A catalytic effect of the buffers was not observed in the oxidation process. An analysis of the dependence of the rate on [H'] reveals that the reactive species under the experimental conditions are periodate monoanion and dianion and the dipolar form of the amino acid. The mechanism proposed and the derived rate law are consistent with the observed kinetics. The rate constants predicted using the derived rate law are in agreement with the observed rate constants, thus justifying this rate law and hence the proposed mechanistic scheme.ROSA PASCUAL et MIGUEL A. HERRAEZ. Can. J. Chem. 63, 2349 (1985). Operant h 10°C et dans un milieu acide, on a CtudiC la cinCtique de l'oxydation de la sCrine et de la thrkonine par le periodate. La rkaction est du premier ordre tant en periodate qu'en acide aminC et I'ensemble de la rkaction est du deuxibme ordre. Les vitesses diminuent avec une augmentation de I'aciditt. On n'a pas observk d'effet catalytique des tampons sur les processus d'oxydation. Une analyse de la relation entre les vitesses de rkaction et la concentration en H' rCvble que les espkces rCactives dans ces conditions expkrimentales sont les monoanion et dianion du periodate et la forme dipolaire de I'acide aminC. Le mCcanisme proposC ainsi que I'Cquation de vitesse qui en dCrive sont en accord avec les cinCtiques observCes. Les constantes de vitesse que I'on peut prCvoir en se basant sur I'Cquation de vitesse que I'on a obtenu sont en accord avec les constantes de vitesses observ6es et ces rksultats justifient cette Cquation de vitesse et donc le schCma mtcanistique proposC.[Traduit par le journal]

Oxidation of l-serine and l-threonine by bis(hydrogen periodato)argentate(III) complex anion: A mechanistic study

“…This character is in contrast to the periodate oxidation reactions in which simultaneous deamination and decarboxylation have been observed [19].…”

“…Kinetics and mechanism for oxidation of L-serine and L-threonine by periodate in acidic media (pH 2.10-5.0) have been reported [19], and the oxidation reactions also follow an overall second-order rate law, first-order in both periodate and the amino acids. The second-order rate constants, derived at 10.0°C, are estimated to be much smaller than those we obtained for the Ag(III) oxidations in the present work.…”

“…Since variation of the concentration of periodate, the coordinated ligand of the silver(III) complex, has a significant influence on the reaction rates for the Ag(III) reactions (vide infra), the interaction between periodate and the amino acids should be checked in the alkaline medium we used in the present work. Reactions between periodate (1-2 mM) and L-serine/L-threonine (10-20 mM) at [OH À ] = 0.020 M and 25.0°C were followed spectrophotometrically at 310 nm, the wavelength used for kinetic measurements in acidic media by Pascual and Herraez [19]. Following the reactions for about 4 h, no significant absorbance changes were observed, indicating that the reactions between periodate and the amino acids were either extremely slow or did not proceed at all in the alkaline medium.…”

“…Some of the oxidants are metal ions/complexes [11][12][13][14][15][16] and others are non-metallic agents [17][18][19][20][21][22]. Although these oxidation reactions display diverse reaction mechanisms, concurrent deamination and decarboxylation to the two amino acids are virtually found in almost all the cases [11][12][13][14][15][16][17][18][19][20][21][22].…”

Kinetics and Mechanism of Oxidation of L-Threonine by Periodate in Alkaline Medium

“…Very few reports are available on the oxidation of L-threonine using peroxydisulphate [1], manganese(VII) [3], N-bromo p-toulenesulphonamide [3], peroxodiphosphate [4], manganese(III) [5,6], bis-(hydrogen periodato)argentite [7], N-bromonicotinamide(NBN) [8], N-chloro p-toulenesulfonamide [9], Chloramine-T [10,11], N-bromophthalimide [12] the product of oxidation is aldehyde and in the oxidation of threonine by hexacyanoferrate(III) [13] the oxidation product is α -ketohydroxybutyric acid. Periodate is a stable two electron oxidant with redox potential of 0.70V [14] in alkaline medium and is a more suitable reagent for the study of oxidation reactions of both organic and inorganic substrates [15][16][17][18][19]. In continuation of our studies on the oxidation of L-threonine by different oxidants [20,21], with an attempt to evaluate its degradation mechanism and products, we have undertaken the kinetics of oxidation of Lthreonine by periodate in alkaline medium.…”