Natori S
Faculty of Pharmaceutical Sciences, University of Tokyo, Japan.
Ciba Found Symp. 1994;186:123-32; discussion 132-4. doi: 10.1002/9780470514658.ch8.
We have isolated and characterized various antimicrobial proteins from the haemolymph of Sarcophaga peregrina (flesh fly) larvae. Of these the sarcotoxin I family is a group of proteins mainly active against Gram-negative bacteria whereas sapecin is active mainly against Gram-positive bacteria. In addition to its function in defence, sapecin also plays a role in insect development. Recently, we identified a hendecapeptide of the sapecin homologue sapecin B that has the same antibacterial activity as the original sapecin B. Both sarcotoxin I and sapecin are inducible proteins synthesized de novo by the fat body and/or haemocytes and secreted into the haemolymph when the insect is in the acute phase response to bacterial infection. Antifungal protein (AFP) is constitutively present in the haemolymph and is active against certain fungi but not bacteria. These various antimicrobial proteins interact with microbial membranes. Sarcotoxin I interferes with membrane functions such as ATP synthesis and amino acid transport. The fungicidal activity of AFP is enhanced synergistically by sarcotoxin I, although sarcotoxin I alone has no appreciable antifungal activity. It is clear that the flesh fly has the ability to mount a potent defence response against microbial parasites by mobilizing several antimicrobial proteins.
我们已经从棕尾别麻蝇（肉蝇）幼虫的血淋巴中分离并鉴定了多种抗菌蛋白。其中，肌毒素I家族是一组主要对革兰氏阴性菌有活性的蛋白质，而天蚕抗菌肽主要对革兰氏阳性菌有活性。除了在防御中的功能外，天蚕抗菌肽在昆虫发育中也起作用。最近，我们鉴定了天蚕抗菌肽同源物天蚕抗菌肽B的一个十一肽，它具有与原始天蚕抗菌肽B相同的抗菌活性。肌毒素I和天蚕抗菌肽都是诱导型蛋白，由脂肪体和/或血细胞重新合成，当昆虫对细菌感染处于急性期反应时分泌到血淋巴中。抗真菌蛋白（AFP）组成性地存在于血淋巴中，对某些真菌有活性，但对细菌无活性。这些各种抗菌蛋白与微生物膜相互作用。肌毒素I干扰膜功能，如ATP合成和氨基酸转运。尽管肌毒素I单独没有明显的抗真菌活性，但抗真菌蛋白的杀真菌活性被肌毒素I协同增强。显然，肉蝇能够通过调动多种抗菌蛋白对微生物寄生虫产生有效的防御反应。
