Substrate Specificity of Aqualysin I, a Bacterial Thermophilic Alkaline Serine Protease fromThermus aquaticusYT-1: Comparison with Proteinase K, Subtilisin BPN′ and Subtilisin Carlsberg
摘要:
Aqualysin I 是从极端嗜热菌栖热菌 YT-1 中分离出来的碱性丝氨酸蛋白酶。我们以 16 种显色琥珀酰三肽对硝基苯胺为底物,分析了 aqualysin I 的动力学性质。我们还比较了 aqualysin I 与蛋白酶 K、枯草杆菌蛋白酶 BPN' 和枯草杆菌蛋白酶 Carlsberg 的底物特异性。我们发现 aqualysin I 在底物结合位点上有 3 个亚位点:S1、S2 和 S3。 S1位点优选丙氨酸和苯丙氨酸。 S2位点优选丙氨酸和正亮氨酸。而S3位点优选苯丙氨酸和异亮氨酸。这些特异性与蛋白酶 K 和枯草杆菌蛋白酶 BPN' 相似。嘉士伯枯草杆菌蛋白酶的特异性不同于其他酶。
A Three-Component Mannich-Type Reaction for Selective Tyrosine Bioconjugation
作者:Neel S. Joshi、Leanna R. Whitaker、Matthew B. Francis
DOI:10.1021/ja0439017
日期:2004.12.1
A new selective bioconjugation reaction is described for the modification of tyrosine residues on protein substrates. The reaction uses imines formed in situ from aldehydes and electron-rich anilines to modify phenolic side chains through a Mannich-type electrophilic aromatic substitution pathway. The reaction takes place under mild pH and temperature conditions and can modify protein substrates at concentrations as low as 20 muM. Using an efficient fluorescence-based assay, we demonstrated the reaction using a number of aldehydes and protein targets. Importantly, proteins lacking surface-accessible tyrosines remained unmodified. It was also demonstrated that enzymatic activity is preserved under the mild reaction conditions. This strategy represents one of the first carbon-carbon bond-forming reactions for protein modification and provides an important complement to more commonly used lysine- and cysteine-based methods.