Production of Glycolate by Oxidation of the 1,2‐Dihydroxyethyl‐thiamin‐diphosphate Intermediate of Transketolase with Hexacyanoferrate(III) or H₂O₂

Abstract

In the presence of hexacyanoferrate(III), or other suitable oxidants, transketolase catalyzes the oxidative cleavage of its donor substrates xylulose 5-phosphate or fructose 6-phosphate into glycolate and glyceraldehyde 3-phosphate or erythrose 4-phosphate, respectively. Two moles of hexacyanoferrate ( Glycolate is also produced with H202 as oxidant; however, the reaction is at least two orders of magnitude slower than with hexacyanoferrate( 111).

Autophagy controls reactive oxygen species homeostasis in guard cells that is essential for stomatal opening

“…We note that a GOX substrate glycolate is provided by conversion not only from the photorespiratory 2-phosphoglycolate (2-PG) metabolism with 2-PG phosphatase (PGLP) but also from glyoxylate with cytosolic and plastidial glyoxylate reductase (GLYR) (40). Glycolate is also produced by the oxidation of the 1,2-dihydroxyethyl-thiamin-diphosphate intermediate of transketolase (41). Conversely, ROS accumulation of cat3-1 and nca1-1 mutants under low light condition was limited compared to that of atg mutants (SI Appendix, Fig.…”

Enzyme-Catalyzed Side Reactions with Molecular Oxygen may Contribute to Cell Signaling and Neurodegenerative Diseases

“…As shown in Fig. 1 (reaction 2), in the course of the overall reaction this carbanionic intermediate undergoes oxidation by the lipoyl residue covalently bound to the second enzyme of the complex, namely E 2 k. However, in a fashion analogous to other ThDP-dependent enzymes [1][2][3], the intermediate may be oxidized by a number of artificial 1e -and 2e -acceptors with very different chemical structures [4,9], suggesting that xenobiotics and/or endogenous electrophiles (e.g., quinones) may also oxidize the E 1 k-generated carbanion in vivo. This may result in the formation of potentially dangerous products and/or paracatalytic inactivation of E 1 k and/or other enzymatic components of KGDHC.…”

“…Depending upon the enzyme, these oxidants included, 2,6-dichloroindophenol, hexacyanoferrate (III), porphyrindin, tetranitromethane, and H 2 O 2 (reviewed in Bunik et al [4]). Philipp Christen coined the word paracatalytic to describe interactions between a carbanionic enzyme intermediate and a reagent (especially an oxidant) not generally considered to be a physiological reactant [1][2][3]. Reactions of enzyme-generated carbanions with O 2 were not included in Christen's original definition of paracatalytic reactions.…”

“…Thirty years ago it was shown that the carbanionic intermediates of several enzymes are accessible to various electrophiles (oxidants) [1][2][3]. Depending upon the enzyme, these oxidants included, 2,6-dichloroindophenol, hexacyanoferrate (III), porphyrindin, tetranitromethane, and H 2 O 2 (reviewed in Bunik et al [4]).…”

A Survey of Oxidative Paracatalytic Reactions Catalyzed by Enzymes that Generate Carbanionic Intermediates: Implications for ROS Production, Cancer Etiology, and Neurodegenerative Diseases

“…Depending on the enzyme, these oxidants included, for example, 2,6-dichloroindophenol (DCIP), hexacyanoferrate(III), porphyrindin, tetranitromethane, and H 2 O 2 (1–8). Christen coined the word paracatalytic to describe enzyme-catalyzed interactions between substrate and a reagent (especially an oxidant) not generally considered to be a physiological reactant (4, 5, 7).…”