Lee M J, Goldsworthy G J, Poulos C P, Velentza A
Department of Biology, Birkbeck College, University of London, UK.
Peptides. 1996;17(8):1285-90. doi: 10.1016/s0196-9781(96)00224-0.
A series of Locusta adipokinetic hormone I (AKH-I), < QLNFTPNWGTa, analogues, were synthesized with modifications at the C-terminal threonine residue using a combination of solid- and liquid-phase methodology and evaluated in Locusta migratoria, in a lipid mobilization assay in vivo and an acetate uptake assay in vitro. Modifications at Thr10 of AKH-I involved replacement of its C-terminal amide by the groups -OH, -OCH3, -NHCH3, -N(CH3)2, and -NHC6H5; the last three groups were also applied to the amide of AKH-I-[Thr(Bzl)10]. The methyl ester, monomethyl, and dimethyl analogues were all of lower activity than the parent in the lipid mobilization assay, but lost less than two orders of potency. In the acetate uptake assay, again the methyl ester analogue showed the greatest retention of biological activity of all modified peptides. A cyclic analogue, cyclo (PLNFTPNWGT), was active in both assays, but only at very high concentrations. Almost all analogues were more active in the acetate uptake assay than in the lipid assay, but unusually, AKH-I-NHCH, and AKH-I-N(CH3)2, together with cyclo(PLNFTPNWGT), were more active in the lipid mobilization assay. In addition, the acid AKH-I analogue did not suffer as large a loss in potency in the lipid mobilization assay as in the acetate uptake assay, although it was less potent in the former. The relative potencies of these two methyl analogues contrast with those for AKH-I[Thr(Bzl)10]-NHCH3 and AKH-I-[Thr(Bzl)10]-N(CH3)2, which, together with both phenyl analogues, were significantly more active in the acetate uptake assay. We conclude that the acetate uptake assay has a greater preference for a hydrophobic C-terminus, compared with the lipid mobilization assay.
利用固相和液相方法相结合，合成了一系列在C端苏氨酸残基处有修饰的飞蝗脂肪动激素I（AKH-I），即<QLNFTPNWGTa类似物，并在飞蝗中进行了体内脂质动员试验和体外乙酸摄取试验评估。AKH-I的Thr10位点修饰包括将其C端酰胺基分别替换为-OH、-OCH3、-NHCH3、-N(CH3)2和-NHC6H5；后三个基团也应用于AKH-I-[Thr(Bzl)10]的酰胺基。在脂质动员试验中，甲酯、单甲基和二甲基类似物的活性均低于母体，但效力损失不到两个数量级。在乙酸摄取试验中，甲酯类似物在所有修饰肽中生物活性保留程度最高。环类似物环（PLNFTPNWGT）在两种试验中均有活性，但仅在非常高的浓度下才有活性。几乎所有类似物在乙酸摄取试验中的活性都高于脂质试验，但不同寻常的是，AKH-I-NHCH和AKH-I-N(CH3)2以及环（PLNFTPNWGT）在脂质动员试验中活性更高。此外，酸性AKH-I类似物在脂质动员试验中的效力损失不像在乙酸摄取试验中那么大，尽管它在前者中的效力较低。这两种甲基类似物的相对效力与AKH-I[Thr(Bzl)10]-NHCH3和AKH-I-[Thr(Bzl)10]-N(CH3)2的相对效力形成对比，后两者与两种苯基类似物在乙酸摄取试验中活性明显更高。我们得出结论，与脂质动员试验相比，乙酸摄取试验对疏水性C端的偏好更大。
