To elucidate the structural requirements for the endotoxic and antagonistic activities of lipid A derivatives, we have focused on the effects of the acyl moieties and acidic groups at the 1- and 4′-positions in the present study. We have synthesized new analogues corresponding to Rubrivivax gelatinosus lipid A, which has a characteristic symmetrical distribution of its acyl groups on its two glucosamine residues with shorter acyl groups (decanoyl groups (C10) and lauryl groups (C12)) than Escherichia coli lipid A’s. Carboxymethyl (CM) analogues in which one of the phosphates was replaced with a CM group were also synthesized with a different distribution of acyl groups. Biological tests revealed that the acyl group distribution in the lipid A analogue, strongly affected its bioactivity. The synthetic Ru. gelatinosus type lipid A showed potent antagonistic activity against LPS, whereas its 1-O-carboxymethyl analogue showed weak endotoxic activity. These results demonstrate that when lipid A has shorter (C10 and C12) hexa-acyl groups, its bioactivity is more easily affected by small structural differences, such as differences in acidic groups or acyl group distribution, and that they can change bioactivity from endotoxic to agonistic or vice versa at this structural boundary for the bioactivity.
为了阐明脂质 A 衍
生物的内毒素和拮抗活性的结构要求,我们在本研究中重点研究了 1-和 4'-位上的酰基部分和酸性基团的影响。我们合成了与 Rubrivivax gelatinosus 脂质 A 相对应的新类似物,其酰基在两个
葡萄糖胺残基上具有特征性对称分布,且酰基(癸酰基 (C10) 和月桂酰基 (C12))比大肠杆菌脂质 A 的更短。还合成了具有不同酰基分布的羧甲基 (CM) 类似物,其中一个
磷酸酯被 CM 基团取代。
生物学测试表明,脂质A类似物中酰基的分布强烈影响其
生物活性。合成Ru。明胶型脂质 A 对 LPS 显示出有效的拮抗活性,而其 1-O-羧甲基类似物则显示出较弱的内毒素活性。这些结果表明,当脂质 A 具有较短的(C10 和 C12)六酰基时,其
生物活性更容易受到微小结构差异的影响,例如酸性基团或酰基分布的差异,并且它们可以将
生物活性从内毒性改变为在该
生物活性的结构边界处是激动的,反之亦然。