The amide and carboxyl groups of bacitracin A

Publisher Website
Google Scholar
Abstract
Bacitracin A and commercial bacitracin have been esterified by treatment with methanolic HC1. About 1/3 of the amide N was removed during esterification. The esterified peptides have been reduced with lithium borohydride and the products hydrolyzed. The composition of the hydrolyzates has been compared with that of similar hydrolyzates of bacitracin A by chromatography and electro-phoresis on paper. Hydrolyzates of the reduced peptide esters contained A -hydroxy- a -aminovaleric acid and small amounts of proline, but no glutamic acid. Hydrolysis of the reduced peptide esters with 12 [image] HC1 at 80[degree] yielded t -(aminosuccinyl) lysine but only traces of aspartic acid. Hydrolysis with 6[image] HC1 at 105[degree] yielded aspartic acid equivalent to one residue and Y-hydroxy- a -aminobutyric acid. It is concluded from these results that the glutamic acid residue in bacitracin A is a-linked and that its Y -carboxyl group is free. It is also concluded that one of the aspartic acid residues in bacitracin A is present as an amide and that both carboxyl groups of the aspartic acid directly linked to the E-amino group of lysine are bound. Alternative structures consistent with these conclusions are discussed.
Keywords