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Lipid degradation in organisms quantified via position-specific carbon isotope analysis of fatty acid
The isotopic composition of organic compounds is defined by the sum of the isotope ratio of the substrates and isotopic fractionation in biosynthesis and degradation processes. Since the 1990s, scientists in biogeochemistry have utilized compound-specific isotope analysis (CSIA) to trace the delivery and to evaluate biosynthetic pathways of organic compounds in natural samples. In the last decade, the CSIA of amino acids has quantified 'degradation' based on the relationship between degradation flux (e.g., deamination) and 15N-enrichment in amino acids, which contributes to the quantitative assessment of "protein (and amino acid) utilization" for diverse organisms and environments. On the other hand, organisms utilize not only proteins (amino acids) but also sugars and lipids in the adaptation to the environmental change and in the response to the growth stage in their life. In the current study, we are challenging the quantification of 'lipid degradation' by using ‘position-specific’ carbon isotope ratios of fatty acids. In this presentation, we would like to share the latest findings, including isotopic fractionation during lipid degradation, a new analytical method, and preliminary data for biological samples. These results will contribute to a better understanding of organisms' physiological responses to environmental changes on the Earth.