Structure of the polyglutamic acid from Bacillus subtilis

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Abstract
Titration of 2 dif-ferent samples of polyglutamic acid from B. subtilis suggests that they are built up exclusively of open peptide chains, and that closed ring structures are not present. When esterified and reduced with lithium borohydride, the products given on subsequent acid hydrolysis show that the glutamic acid residues in the polypeptide are exclusively [gamma] -linked and that the presence of branch chains is unlikely. The properties of the ester, the extent of reduction achieved and the composition of the hydrolysate of the reduced ester are dependent in an unusual way on whether the degree of esterification is less than 93% or exceeds this value. It is suggested that this difference in ester behavior can be correlated with the number of residual carboxyl groups present.