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Fractionation of carbon ( 13 C/ 12 C) isotopes in glycine decarboxylase reaction
Author(s) -
Ivlev A.A.,
Bykova N.V.,
Igamberdiev A.U.
Publication year - 1996
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(96)00421-8
Subject(s) - decarboxylation , glycine , chemistry , fractionation , photosynthesis , kinetic isotope effect , isotopes of carbon , biochemistry , amino acid , organic chemistry , deuterium , physics , quantum mechanics , total organic carbon , catalysis
Fractionation of carbon isotopes ( 13 C/ 12 C) by glycine decarboxylase (GDC) was investigated in mitochondrial preparations isolated from photosynthetic tissues of different plants ( Pisum, Medicago, Triticum, Hordeum, Spinacia, Brassica, Wolffia ). 20 mM glycine was supplied to mitochondria, and the CO 2 formed was absorbed and analyzed for isotopic content. CO 2 evolved by mitochondria of Pisum was enriched up to 8% in 12 C compared to the carboxylic atom of glycine. CO 2 evolved by mitochondria of the other plants investigated was enriched by 5–16 % in 13 C. Carbon isotope effects were sensitive to reaction conditions (pH and the presence of GDC cofactors). Theoretical treatment of the reaction mechanism enabled us to conclude that the value and even the sign of the carbon isotope effect in glycine decarboxylation depend on the contribution of the enzyme‐substrate binding step and of the decarboxylation step itself to the overall reaction rate. Therefore, the fractionation of carbon isotopes in GDC reaction was revealed which provides essential isotopic effects in plants in addition to the well‐known effect of carbon isotope fractionation by the central photosynthetic enzyme, ribulose‐1,5‐biphosphate carboxylase.