Biochemical and physiological determinants of intramolecular isotope patterns in sucrose from C-3, C-4 and CAM plants accessed by isotopic C-13 NMR spectrometry: a viewpoint

This paper discusses the biochemical and physiological factors underlying the site-specific, non-random distribution of C-13/C-12 isotope ratios within plant metabolites, which can be determined by isotopic C-13 NMR spectrometry. It focuses on the key metabolite glucose and on enzyme activities and physiological processes that are responsible for the carbon isotope patterns in glucose from different biological origins. It further considers how intramolecular C-13/C-12 isotope ratios in glucose can be exploited to understand fundamental aspects of plant biological chemistry, how these are related to environmental parameters and how these influence metabolites beyond central sugar metabolism. It does not purport to be an extensive overview of intramolecular isotopic patterns. Rather, the aim is to show how a full understanding of C-12/C-13 fractionations occurring during plant metabolism can only be possible once the factors that define intramolecular isotope values are better delineated