Department of Fruit Trees and Wood Plant Sciences, University of Bologna, viale Fanin 46, 40127 Bologna, Italy.
Environ Microbiol. 2009 Dec;11(12):3087-95. doi: 10.1111/j.1462-2920.2009.02013.x. Epub 2009 Jul 23.
Six position-specific (13)C-labelled isotopomers of glucose were supplied to the ectomycorrhizal fungi Suillus pungens and Tricholoma flavovirens. From the resulting distribution of (13)C among fungal PLFAs, the overall order and contribution of each glucose atom to fatty acid (13)C enrichment was: C6 (approximately 31%) > C5 (approximately 25%) > C1 (approximately 18%) > C2 (approximately 18%) > C3 (approximately 8%) > C4 (approximately 1%). These data were used to parameterize a metabolic model of the relative fluxes from glucose degradation to lipid synthesis. Our data revealed that a higher amount of carbon is directed to glycolysis than to the oxidative pentose phosphate pathway (60% and 40% respectively) and that a significant part flows through these pathways more than once (73%) due to the reversibility of some glycolysis reactions. Surprisingly, 95% of carbon cycled through glyoxylate prior to incorporation into lipids, possibly to consume the excess of acetyl-CoA produced during fatty acid turnover. Our approach provides a rigorous framework for analysing lipid biosynthesis in fungi. In addition, this approach could ultimately improve the interpretation of isotopic patterns at natural abundance in field studies.
将六种位置特异性的（13）C 标记葡萄糖同位素给外生菌根真菌苏力菌和黄褐牛肝菌进行供应。根据真菌 PLFA 中（13）C 的分布情况，可以确定每个葡萄糖原子对脂肪酸（13）C 富集的总体顺序和贡献程度为：C6（约 31%）>C5（约 25%）>C1（约 18%）>C2（约 18%）>C3（约 8%）>C4（约 1%）。这些数据被用于对从葡萄糖降解到脂质合成的相对通量的代谢模型进行参数化。我们的数据表明，有更多的碳被定向用于糖酵解而不是氧化戊糖磷酸途径（分别为 60%和 40%），并且由于一些糖酵解反应的可逆性，这些途径中的一部分会多次通过（73%）。令人惊讶的是，95%的碳在被掺入脂质之前循环通过乙醛酸途径，这可能是为了消耗脂肪酸周转过程中产生的多余乙酰辅酶 A。我们的方法为分析真菌中的脂质生物合成提供了严格的框架。此外，这种方法最终可以改善在野外研究中对自然丰度同位素模式的解释。
