【摘要】 Asn-Ala-Gly-Ala 四肽是从人脑分离出来的具有镇痛活性的多肽。为了阐明此活性肽生物活性的基本结构特征,曾合成了一系列的类似物并进行其活力测定。结果表明:该活性四肽的N-端三肽即Asn-Ala-Gly 和活性四肽向C-端引伸一个Asn 残基的五肽即Asn-Ala-Gly-Ala-AsnNH₂均有相似的镇痛活性,而第二位Ala 为D-Ala 取代的四肽类似物Ash-DAla-Gly-Ala 亦具有相近的镇痛活力,然维持的时间较活性四肽为长。如N-端从Asn 再延伸一个氨基酸残基或将活性四肽的顺序加以任何改变均导致镇痛活力的全部丧失。因此此活性四肽的基本结构为专一的四肽即Asn-Ala-Gly-Ala。由于此四肽的氨基酸顺序和人的β-LPH 的第14位至18位顺序相同,曾猜测是否有可能β-LPH 是此活性肽的前体。从合成牛的β-LPH14位至18位五肽即Glu-Ala-Pro-Ala-Glu 不表现镇痛活力这点说明可能此活性肽并不与β-LPH 有任何前体的关系。更多还原

【Abstract】 Asn-Ala--Gly-Ala,an interesting tetrapeptide isolated from human brain,hasbeen found to show strong analgesic effects.In order to elucidate the basic structuralfeature for such biological activity a series of analogs have been prepared and assayedby the usual methods.Among those analogs studied only the N-terminal tripeptide,Asn-Ala-Gly and the pentapeptide amide,Asn-Ala-Gly-Ala-Asn-NH₂,showed ana-lgesic activities of the same order as that of the tetrapeptide,while the analog Asn-D-Ala-Gly-Ala showed the same effect but with prolonged duration.An extra aminoacid on the N-terminus or a change of order of the sequence of the tetrapeptide willresult in the total loss of biologioal activity.Thus,the structural feature for analgesicaction is very specifically exclusive in Asn-Ala-Gly-Ala.Due to the identity of this tetrapeptide sequence with the sequence 14～17 ofhuman β-lipotropin,the corresponding sequence（14～18）of bovine β-lipotropin,Glu-Ala-Pro-Ala-Glu,was prepared and found to exhibit no analgesic activity.Thisindicates that no correlation should be assigned for a preourseractive prinoiplo relati,onship.更多还原