Fractionation of carbon (13C/12C) isotopes in glycine decarboxylase reaction

FEBS Letters

Igamberdiev, A.U.²  Ivlev, A.A.¹  Bykova, N.V.² 

[1]All-Russian Institute for Petroleum Geology, Shosse Entuziastov 36, Moscow 105819, Russian Federation

[2]Department of Plant Physiology and Biochemistry, Voronezh State University, Voronezh 394693, Russian Federation

关键词: Glycine decarboxylase complex;    Isotope fractionation;    Photorespiration;    Plant mitochondria;   

DOI  :  10.1016/0014-5793(96)00421-8

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Fractionation of carbon isotopes (¹³C/¹²C) 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 CO₂ formed was absorbed and analyzed for isotopic content. CO₂ evolved by mitochondria of Pisum was enriched up to 8% in ¹²C compared to the carboxylic atom of glycine. CO₂ evolved by mitochondria of the other plants investigated was enriched by 5–16 % in ¹³C. 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.

【 授权许可】

Unknown