An approach to chemical phylogeny is discussed, based on an emphasis on alterations of biosynthetic pathways rather than on isolations of individual compounds. Some offshoots of biosynthetic pathways to target molecules such as gibberellic acid are considered. Attempts are made to assess the significance of alterations of pathways in terms of the chemical probabilities of their occurrences. Attempts have been made to assist that essentially artificial dassification, taxonomy, by considering the structures of plant constituents as markers on a level with morphological characteristics. This is quite legitimate, but both taxonomy and its much more fundamental relative phylogeny may weil be illuminated much more by considerations of biosynthetic pathways than of individual structures. Some tentative attempts have been made but there appears tobe required a more systematic analysis of the whole situation. The constituents of plants and microorganisms can be divided roughly into two categories; molecules which are of primary metabolic and structural importance, and molecules of secondary, or no known, functions. The first dass contains small molecules which appear to be ubiquitous, such as sugars, amino acids, citric acid, etc., which are the universal building blocks and energy sources. It also contains proteins, nucleic acids, polysaccharides, etc., which may differ in structural details from one organism to another but which appear to have universal types of function as enzymes, structural materials and carriers of hereditary mechanisms. More arguable as to category are rather specialized structural materials characteristic of dasses of whole organisms rather than of individual cells, such as Iignin. The secondary category indudes a great diversity of chemical types, usually in fairly small molecules, with a sporadic occurrence. Although the first dass is a more fundamental one, and undoubtedly will be examined in structural terms to define relations between organisms in a way which has already been done, for example, with the globin portion of haemoglobins, the task is much more difficult because of the great molecular complexity · involved and because of the universal distribution of types in which alterations may be small, for example, the replacement of one amino acid by another in a molecule containing many such units.

中文翻译：

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化学系统发育中的生物合成途径

讨论了一种化学系统发育的方法，其基础是强调生物合成途径的改变，而不是单个化合物的分离。考虑到目标分子（如赤霉酸）的生物合成途径的一些分支。尝试根据其发生的化学概率来评估途径改变的重要性。已经尝试通过将植物成分的结构视为具有形态特征的水平上的标记来帮助基本上人工的分类、分类。这是非常合理的，但是分类学及其更基本的相对系统发育可能更多地通过考虑生物合成途径而不是单个结构来阐明。已经进行了一些试探性的尝试，但似乎需要对整个情况进行更系统的分析。植物和微生物的成分大致可分为两类；具有初级代谢和结构重要性的分子，以及具有次级或未知功能的分子。第一个 dass 包含似乎无处不在的小分子，如糖、氨基酸、柠檬酸等，它们是通用的积木和能源。它还包含蛋白质、核酸、多糖等，它们在结构细节上可能因一种生物体而异于另一种生物体，但它们似乎具有作为酶、结构材料和遗传机制载体的通用类型的功能。关于类别更有争议的是整个生物体的细胞特征的相当专业的结构材料，而不是单个细胞的特征，例如 Iignin。第二类包括化学类型的多样性，通常是相当小的分子，偶尔出现。虽然第一个 dass 是一个更基本的，毫无疑问将在结构方面进行检查，以一种已经完成的方式来定义生物体之间的关系，例如，使用血红蛋白的珠蛋白部分，这项任务要困难得多，因为· 涉及巨大的分子复杂性，并且由于类型的普遍分布，其中改变可能很小，例如，在包含许多此类单元的分子中，一种氨基酸被另一种氨基酸替换。