A new insight into isotopic fractionation associated with decarboxylation in organisms: implications for amino acid isotope approaches in biogeoscience

Progress in Earth and Planetary Science

Table 3 Possible factors for controlling trophic discrimination (Δ) and key reactions responsible for isotopic fractionation (ε) on consumers

	Possible factor for Δ of an amino acid		Key reaction responsible for ε of an amino acid		Classification of amino acids
	Nitrogen	Carbon	Nitrogen	Carbon	Classification of amino acids
Aromatic	-	-	-	-	Source -Essential
Branched	Deamination flux of the amino acid	-	Deamination of the amino acid	-	Trophic -Essential
Others	Balance between deamination and biosynthetic flux of the amino acid	Biosynthetic flux of the amino acid	Deamination of the amino acid	Decarboxylation of the precursor (e.g., pyruvic acid and α-ketoglutaric acid)	Trophic -Nonessential