Studies on the Metabolism of Free Amino Acids during Maturation and Ripening of Tomato Fruits

Abstract

The experiments were carried out to clarify the metabolism of glutamic acid (Glu) and γ-aminobutyric acid (γ-ABA) and the changes of their metabolism during the ripening of tomato fruits. As a result of the experiment using L-Glu-14C (U) and γ-ABA-1-14C in tomato slices, Glu was converted into γ-ABA by decarboxylation and γ-ABA was metabolized into the acids in TCA cycle. The 14C-activity incorporated in the acids from γ-ABA-1-14C was higher in succinic and malic acids. This incorporation rate was higher in immature stages and decreased with ripening.These results suggested that the metabolic pathway of Glu to succinate via γ- ABA (and succinic semialdehyde) existed and this pathway might play an important role in ripening process of tomato fruits as a by-pass of the α-ketoglutarate-suc cinate step of the TCA cycle.