H. Itano, E. Robinson
Aug 10, 1972
Citations
0
Influential Citations
25
Citations
Journal
The Journal of biological chemistry
Abstract
Abstract A new basic α-amino acid with a quaternary ammonium side chain was synthesized in high yield by trimethylaminoethylation of l-cysteine with (2-bromoethyl)trimethylammonium (BETA) bromide at pH 9.1. The amino acid, l-[2-[(2-amino-2-carboxyethyl)thio]ethyl]trimethylammonium hydroxide, inner salt, is named 4-thialaminine or thialaminine. It was purified as crystals of bromide hydrobromide, bromide hydrobromide (2:1), and chloride hydrochloride. The N2-p-tolylsulfonyl derivative and esters of this derivative were also prepared. (2-Iodoethyl)trimethylammonium nitrate reacted nearly as rapidly as BETA bromide with cysteine, but (2-chloroethyl)trimethylammonium chloride reacted very slowly. Treatment of dithiothreitol-reduced proteins with BETA bromide resulted in quantitative conversion of cysteine residues to 4-thialaminine without significant reduction in content of other amino acid residues. Thialaminine was found to be extremely stable under the usual conditions of acid hydrolysis of proteins and eluted between lysine and histidine in the amino acid analyzer. In contrast to most products of reduction and alkylation or of S-sulfonation of proteins, reduced and trimethylaminoethylated proteins were readily soluble in water. Thialaminyl peptide bonds were resistant to the action of trypsin; on the other hand, the chymotryptic activity of trypsin toward certain bonds of trimethylaminoethylated insulin was enhanced.