Experimental observations, accumulated during several decades, have allowed an overall scheme for the biosynthesis of the mycolic acids, which are very long chain fatty acids of Mycobacteria to be proposed. But, in almost every step, several hypotheses are compatible with the experimental results, leading to variations of the overall scheme. The aim of this review is to point to some additional possibilities. It is generally assumed that the classical elongation process of fatty acid synthesis produces two long chains, the condensation of which leads to the direct precursors of mycolic acids. But three condensations of four fatty acids, usually synthesized by Mycobacteria, is another hypothesis that could be considered. In the first hypothesis, some methyl or methylene substituents or oxygenated functions are added to the double bonds of an unsaturated precursor, whereas in the second hypothesis, the methylations could help in the building of very long aliphatic chains, and determine the location of double bonds or ramifications. The hypothetical coexistence of two pathways for mycolate biosynthesis is discussed.

中文翻译：

---

分枝杆菌对霉菌酸的生物合成：当前假说和其他假说。

在几十年中积累的实验观察结果已经提出了分枝杆菌酸生物合成的总体方案，分枝杆菌酸是分枝杆菌的非常长的脂肪酸。但是，几乎在每个步骤中，都有几种假设与实验结果兼容，从而导致整个方案有所不同。这次审查的目的是指出一些其他可能性。通常认为，脂肪酸合成的经典延伸过程产生两条长链，其缩合导致霉菌酸的直接前体。但是通常可以通过分枝杆菌合成的四种脂肪酸的三缩合是另一个可以考虑的假设。在第一个假设中 一些甲基或亚甲基取代基或含氧官能团被添加到不饱和前体的双键上，而在第二个假设中，甲基化可以帮助建立很长的脂族链，并确定双键或分支的位置。讨论了两种路线的假设性共存。