氨基酸是生命物质中普遍存在的一类重要的有机化合物,它是构成蛋白质的“砖块”。一个最简单的氨基酸分子至少必须含有一个羧基和一个氨基的官能团。在生物的蛋白质中通常只包括有二十种氨基酸,叫做蛋白氨基酸。但是自然界还存在其它种类的氨基酸,因为它们一般不存在于蛋白质中,所以叫做非蛋白氨基酸。除了最简单的甘氨酸外,所有的氨基酸都含有一个以上的不对称的碳原子。含有一个不对称碳原子的氨基酸可以存在L和D型两种结构的对映体。所有的蛋白质氨基酸都属L构型。另外有四种氨基酸,它们含有两个不对称的碳原子,因此可以有两种对映的异构体,而且,还可以有两种非对映的 Amino acids are an important class of organic compounds that are ubiquitous in living matter and constitute “bricks” of proteins. A simple amino acid molecule must contain at least one carboxyl and one amino functional group. In biological proteins usually include only twenty amino acids, called protein amino acids. But there are other kinds of amino acids in nature, because they are generally not present in the protein, so called non-protein amino acids. With the exception of the simplest glycines, all amino acids contain more than one asymmetric carbon atom. Amino acids that contain an asymmetric carbon atom can exist as enantiomers of both the L and D forms. All protein amino acids are L configurations. There are four other amino acids, which contain two asymmetric carbon atoms, so there are two enantiomeric isomers, but two diastereomeric