Effects of amino acid sequence, buffers, and ionic strength on the rate and mechanism of deamidation of asparagine residues in small peptides.
Effects of amino acid sequence, buffers, and ionic strength on the rate and mechanism of deamidation of asparagine residues in small peptides.
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DOI：
10.1016/s0021-9258(18)54607-x
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发表时间：
1991-11
期刊：
影响因子：
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通讯作者：
R. Tyler-Cross;Verne SchirchS
中科院分区：
文献类型：
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作者：
R. Tyler-Cross;Verne SchirchS
Asn残基脱酰胺的非酶速率在一系列的五肽序列VSNXV和VXNSV，其中X是10个不同的氨基酸之一，测定在中性，碱性和酸性pH值。结果表明，在中性和碱性溶液中，Asn氨基侧的氨基酸残基对脱酰胺速率几乎没有影响，无论其电荷或大小如何。天冬酰胺羧基侧的基团对脱酰胺速率有显著影响。与具有最大脱酰胺速率的N-G序列中的甘氨酸相比，该残基的侧链中的增加的大小和分支使脱酰胺速率降低多达70倍。在酸性溶液中，天冬酰胺残基的脱酰胺速率不受肽的氨基酸序列的影响。检测各脱酰胺反应产物中isoAsp残基的形成。在中性和碱性溶液中，所有产物均显示isoAsp：Asp肽产物以约3：1的比例形成。在酸性溶液中，Asp肽是形成的唯一脱酰胺产物。发现所有其中Ser残基跟随Asn残基的肽在中性和碱性溶液中经历肽裂解反应，产生三肽和二肽。在中性和碱性pH值下，裂解反应的速率约为脱酰胺途径速率的10%。所研究的肽中Asn残基的脱酰胺速率不受离子强度的影响，并且不受特定碱催化。对于小碱如氨，观察到一般碱催化。脱酰胺反应的模型，提出了考虑到所观察到的效果。
The nonenzymatic rates of deamidation of Asn residues in a series of pentapeptides with the sequences VSNXV and VXNSV, where X is one of 10 different amino acids, were determined at neutral, alkaline, and acid pH values. The results demonstrate that in neutral and alkaline solutions the amino acid residue on the amino side of the Asn had little or no effect on the rate of deamidation regardless of its charge or size. The group on the carboxyl side of Asn affected the rate of deamidation significantly. Increasing size and branching in the side chain of this residue decreased the rate of deamidation by as much as 70-fold compared to glycine in the N-G sequence, which had the greatest rate of deamidation. In acidic solution, the rate of deamidation of the Asn residue was not affected by the amino acid sequence of the peptide. The products for each deamidation reaction were tested for the formation of isoAsp residues. In neutral and alkaline solutions, all products showed that the isoAsp:Asp peptide products were formed in about a 3:1 ratio. In acidic solution, the Asp peptide was the only deamidation product formed. All peptides in which a Ser residue follows the Asn residue were found to undergo a peptide cleavage reaction in neutral and alkaline solutions, yielding a tripeptide and a dipeptide. The rate of the cleavage reaction was about 10% of the rate of the deamidation pathway at neutral and alkaline pH values. The rates of deamidation of Asn residues in the peptides studied were not affected by ionic strength, and were not specific base catalyzed. General base catalysis was observed for small bases like ammonia. A model for the deamidation reaction is proposed to account for the observed effects.