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青霉素和头孢菌素之所以具有强大的抗菌作用,是由于它们能与细菌合成其细胞壁的转肽酶发生不可逆的结合,使转肽酶丧失活性,中断了合成细胞壁的生化过程。细菌由于不能正常合成保护其自身的细胞壁而崩解死亡。这种结合之所以可能,是因为青霉素、头孢菌素在化学结构上与转肽酶的作用废物——丙氨酰丙氨酸(粘肽的末端结构)有相似的空间构型所致。这可从图1直观地看出。
The reason why penicillins and cephalosporins have a strong antibacterial effect is that they irreversibly bind to the transpeptidase that bacteria synthesize in their cell walls, rendering the transpeptidase inactive and disrupting the biochemical process of synthetic cell walls. Bacteria disintegrate and die because they can not normally synthesize and protect their own cell walls. This combination is probably due to the similar spatial configuration of penicillins and cephalosporins that are chemically identical to the transpeptidase-alanyl-alanine (the terminal structure of the mucolytic peptide). This can be seen visually in Figure 1.