Histidine chemical modification reagents

Chemical modifications of proteins (enzymes) by reacting them with iV-acylimidazoles are a way of studying active sites. By this means the amino acid residues (e.g., tyrosine, lysine, histidine) essential for catalytic activity are established on the basis of acylation with the azolides and deacylation with other appropriate reagents (e.g., hydroxylamine). 

Classical approaches to chemical enzyme modification, however, often suffer from lack of regio-selectivity, which can yield heterogeneous and irreproducible enzyme mixtures. For example, preparation of methyl-chymotrypsin, -subtilisin or -trypsin using methyl sulfonate reagents, originally used to methylate the histidine of the... 

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