Coolican S A, Gurd R S
Arch Biochem Biophys. 1984 Aug 1;232(2):450-7. doi: 10.1016/0003-9861(84)90561-7.
N alpha-Maltoglucagon was prepared by demethylation of N alpha-malto, S-methyl methionine27 glucagon, and the two derivatives were purified to greater than 99% and 99.7%, respectively. S-Methylation of glucagon lowers the reactivity of Lys-12 and provides an alternative strategy to epsilon-amino protection for directing glycosylation of glucagon to the alpha-amino group. Both derivatives are partial agonists, with their adenylate cyclase activation and binding reduced in parallel. N alpha-Maltoglucagon produces 70% and N alpha-malto, S-methyl methionine27 glucagon 40% of the maximum activity of native hormone. N alpha-Maltoglucagon binds equivalently to N alpha-biotinyl, N epsilon-acetimidoglucagon whose maximum activity is near 35%, but a pK shift of the imidazole moiety cannot account for the difference in their abilities to produce transduction. Both glycosylated derivatives bind noncooperatively and both inhibit adenylate cyclase at high concentrations. The presence of a maltose residue on the amino terminal of glucagon may be required but, alone provides insufficient structural complementarity for concanavalin A binding to occur. The glycosylated derivatives are resistant to aminopeptidase degradation, are more soluble, and the maltose residue is unlikely to cause toxicity with in vivo use. Such attributes may be advantageous in the development of other analogs.
通过对Nα-麦芽糊精、S-甲基蛋氨酸27胰高血糖素进行去甲基化反应制备了Nα-麦芽糊精胰高血糖素，两种衍生物的纯度分别达到了99%以上和99.7%。胰高血糖素的S-甲基化降低了赖氨酸-12的反应活性，并提供了一种ε-氨基保护的替代策略，用于将胰高血糖素的糖基化导向α-氨基。两种衍生物都是部分激动剂，它们的腺苷酸环化酶激活和结合能力同时降低。Nα-麦芽糊精胰高血糖素产生的活性为天然激素最大活性的70%，Nα-麦芽糊精、S-甲基蛋氨酸27胰高血糖素产生的活性为40%。Nα-麦芽糊精胰高血糖素与最大活性接近35%的Nα-生物素化、Nε-乙酰亚胺基胰高血糖素的结合能力相当，但咪唑部分的pK值变化不能解释它们产生转导能力的差异。两种糖基化衍生物均以非协同方式结合，且在高浓度时均抑制腺苷酸环化酶。胰高血糖素氨基末端存在麦芽糖残基可能是必需的，但仅靠它提供的结构互补性不足以使伴刀豆球蛋白A发生结合。糖基化衍生物对氨肽酶降解具有抗性，更易溶解，且麦芽糖残基在体内使用时不太可能引起毒性。这些特性在开发其他类似物时可能具有优势。
