Biosynthetic origin of the saw-toothed profile in d13C and d2Y of n-alkanes and systematic isotopic differences between n-, iso- and anteiso-alkanes in leaf waxes of land plants
The n-fatty acids containing an even number of carbons (ECN-n-FAs) in higher plants are iosynthesisedby repetitive addition of a two carbon unit from malonyl-ACP. The n-alkanes containing an odd numberof carbon atoms (OCN-n-alkanes) are generally formed by the decarboxylation of ECN-n-FAs, but it is...
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| Format: | Journal Article |
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elsevier
2010
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| Online Access: | http://hdl.handle.net/20.500.11937/14797 |
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| author | Zhou, Y. Grice, Kliti Stuart-Williams, H. Farquhar, G. Hocart, C. Lu, H. Liu, W. |
| author_facet | Zhou, Y. Grice, Kliti Stuart-Williams, H. Farquhar, G. Hocart, C. Lu, H. Liu, W. |
| author_sort | Zhou, Y. |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | The n-fatty acids containing an even number of carbons (ECN-n-FAs) in higher plants are iosynthesisedby repetitive addition of a two carbon unit from malonyl-ACP. The n-alkanes containing an odd numberof carbon atoms (OCN-n-alkanes) are generally formed by the decarboxylation of ECN-n-FAs, but it isunknown how the less abundant even-carbon-numbered alkanes (ECN-n-alkanes) are biosynthesisedin higher plants. There is a distinctive compositional pattern of incorporation of stable carbon (13C) and hydrogen (2H) isotopes in co-existing ECN- and OCN-n-alkanes in leaves of higher plants, such that the OCN n-alkanes are relatively enriched in 13C but relatively depleted in 2H against the ECN-n-alkanes. This is consistent with the OCN-n-fatty acids having a propionate precursor which is derived from reduction of pyruvate. A tentative pathway is presented with propionate produced by enzymatic reduction of pyruvate which is then thio-esterified with CoSH (coenzyme A thiol) in the chloroplast to form the terminal precursor molecule propionyl-CoA. This is then repetitively extended/elongated with the 2-carbon unit from malonyl-ACP to form the long chain OCN-n-fatty acids. The anteiso- and iso-alkanes in Nicotiana tabacum leaf waxes have previously been found to be systematically enriched in 13C compared with the n-alkanes by Grice et al. (2008). This is consistent with the isotopic composition of their putative respective precursors (pyruvate as precursor for n-alkanes, valinefor iso-alkanes and isoleucine for anteiso-alkanes). The current study complements that of Grice et al.(2008) and looks at the distribution of hydrogen isotopes. The n-alkanes were found to be more enrichedin deuterium (2H) than the iso-alkanes which in turn were more enriched than the anteiso-alkanes. Wepropose therefore that the depletion of 2H in the iso-alkanes, relative to the n-alkanes is the consequence of accepting highly 2H-depleted hydrogen atoms from NADPH during their biosynthesis. The anteisoalkanes are further depleted again because there are three NADPH-derived hydrogen atoms in their precursor isoleucine, as compared with only one NADPH-derived hydrogen in valine, the precursor of the isoalkanes. |
| first_indexed | 2025-11-14T07:09:30Z |
| format | Journal Article |
| id | curtin-20.500.11937-14797 |
| institution | Curtin University Malaysia |
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| last_indexed | 2025-11-14T07:09:30Z |
| publishDate | 2010 |
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| spelling | curtin-20.500.11937-147972017-09-13T15:55:19Z Biosynthetic origin of the saw-toothed profile in d13C and d2Y of n-alkanes and systematic isotopic differences between n-, iso- and anteiso-alkanes in leaf waxes of land plants Zhou, Y. Grice, Kliti Stuart-Williams, H. Farquhar, G. Hocart, C. Lu, H. Liu, W. Stable carbon isotopes iso-Alkanes Biosynthetic precursors Stable hydrogen isotopes anteiso-Alkanes The n-fatty acids containing an even number of carbons (ECN-n-FAs) in higher plants are iosynthesisedby repetitive addition of a two carbon unit from malonyl-ACP. The n-alkanes containing an odd numberof carbon atoms (OCN-n-alkanes) are generally formed by the decarboxylation of ECN-n-FAs, but it isunknown how the less abundant even-carbon-numbered alkanes (ECN-n-alkanes) are biosynthesisedin higher plants. There is a distinctive compositional pattern of incorporation of stable carbon (13C) and hydrogen (2H) isotopes in co-existing ECN- and OCN-n-alkanes in leaves of higher plants, such that the OCN n-alkanes are relatively enriched in 13C but relatively depleted in 2H against the ECN-n-alkanes. This is consistent with the OCN-n-fatty acids having a propionate precursor which is derived from reduction of pyruvate. A tentative pathway is presented with propionate produced by enzymatic reduction of pyruvate which is then thio-esterified with CoSH (coenzyme A thiol) in the chloroplast to form the terminal precursor molecule propionyl-CoA. This is then repetitively extended/elongated with the 2-carbon unit from malonyl-ACP to form the long chain OCN-n-fatty acids. The anteiso- and iso-alkanes in Nicotiana tabacum leaf waxes have previously been found to be systematically enriched in 13C compared with the n-alkanes by Grice et al. (2008). This is consistent with the isotopic composition of their putative respective precursors (pyruvate as precursor for n-alkanes, valinefor iso-alkanes and isoleucine for anteiso-alkanes). The current study complements that of Grice et al.(2008) and looks at the distribution of hydrogen isotopes. The n-alkanes were found to be more enrichedin deuterium (2H) than the iso-alkanes which in turn were more enriched than the anteiso-alkanes. Wepropose therefore that the depletion of 2H in the iso-alkanes, relative to the n-alkanes is the consequence of accepting highly 2H-depleted hydrogen atoms from NADPH during their biosynthesis. The anteisoalkanes are further depleted again because there are three NADPH-derived hydrogen atoms in their precursor isoleucine, as compared with only one NADPH-derived hydrogen in valine, the precursor of the isoalkanes. 2010 Journal Article http://hdl.handle.net/20.500.11937/14797 10.1016/j.phytochem.2009.11.009 elsevier restricted |
| spellingShingle | Stable carbon isotopes iso-Alkanes Biosynthetic precursors Stable hydrogen isotopes anteiso-Alkanes Zhou, Y. Grice, Kliti Stuart-Williams, H. Farquhar, G. Hocart, C. Lu, H. Liu, W. Biosynthetic origin of the saw-toothed profile in d13C and d2Y of n-alkanes and systematic isotopic differences between n-, iso- and anteiso-alkanes in leaf waxes of land plants |
| title | Biosynthetic origin of the saw-toothed profile in d13C and d2Y of n-alkanes and systematic isotopic differences between n-, iso- and anteiso-alkanes in leaf waxes of land plants |
| title_full | Biosynthetic origin of the saw-toothed profile in d13C and d2Y of n-alkanes and systematic isotopic differences between n-, iso- and anteiso-alkanes in leaf waxes of land plants |
| title_fullStr | Biosynthetic origin of the saw-toothed profile in d13C and d2Y of n-alkanes and systematic isotopic differences between n-, iso- and anteiso-alkanes in leaf waxes of land plants |
| title_full_unstemmed | Biosynthetic origin of the saw-toothed profile in d13C and d2Y of n-alkanes and systematic isotopic differences between n-, iso- and anteiso-alkanes in leaf waxes of land plants |
| title_short | Biosynthetic origin of the saw-toothed profile in d13C and d2Y of n-alkanes and systematic isotopic differences between n-, iso- and anteiso-alkanes in leaf waxes of land plants |
| title_sort | biosynthetic origin of the saw-toothed profile in d13c and d2y of n-alkanes and systematic isotopic differences between n-, iso- and anteiso-alkanes in leaf waxes of land plants |
| topic | Stable carbon isotopes iso-Alkanes Biosynthetic precursors Stable hydrogen isotopes anteiso-Alkanes |
| url | http://hdl.handle.net/20.500.11937/14797 |