The use of lntramolecular carbon isotope distributions (13c/12c) of biomolecules to study temporal organization of post-photosynthetic metabolism in a plant cell

Ivlev AA

It was found that the pyruvate decarboxylation reaction (PDR) plays a key role in post-photosynthetic metabolism, and PDR products are structural units involved in the synthesis of almost all its metabolites [1,2]. Carbon atoms of PDR products (marker atoms) make up the carbon skeletons of metabolites. Here we show that analysis of isotope fractionation in PDR makes it possible to estimate the isotopic composition of each marker atom and its dependence on two factors: 1) on the kinetic isotopic effect of C – C bond cleavage and 2) on the isotopic effect when the pyruvate pool is depleted (Raleigh isotope effect). It is also shown that marker atoms can be divided into three groups. The first group includes atoms of methyl groups of acetate (C2-) fragments and atoms of pyruvate (C3 fragments) subjected to decarboxylation. Their carbon isotope composition does not change during decarboxylation and can serve as an internal standard. The second group includes the carbon atom of CO2 and the acyl-carbon atom of С2 – fragments. According to the kinetic isotope effect theory, they may be either enriched in 12C. relative to the atoms of the first group, when pyruvate pool depletion is less than 50% or enriched in 13C when pyruvate pool depletion is more than 50%. The third group includes the acyl and adjacent carboxyl atoms of the residual pyruvate, located at the ends of the cleaved C - C bond. These atoms are always enriched in 13C as compared with the atoms of the first and second groups at the same extent of pyruvate pool depletion. The comparison of the theoretically expected distribution of marker atoms and the experimentally measured isotope distribution of carbon atoms in the metabolites allows for studying the structural and temporal organization of post-photosynthetic metabolism.

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Published on: Dec 12, 2022 Pages: 11-16

Full Text PDF Full Text HTML DOI: 10.17352/ab.000006
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