Enzymatically catalysed decarboxylation of β-carboxyaspartic acid (Asa)

A better synthetic route to β-carboxyaspartic acid (Asa) was achieved through condensation of sodium dibenzyl malonate and benzyl 2-bromoacetate as an alternative to two steps in the method of Koch etal. Catalytic hydrogenation at 5 atm pressure in a shaken stainless steel vessel removed protecting carbobenzyloxy groups. Asa was purified on a cation exchange column. An extract of E. coli was found to catalyse the decarboxylation of Asa in a doubly coupled assay designed to be specific for produced aspartic acid. Evidence for enzymatic decarboxylation includes complete loss of activity on boiling and progressive loss of activity on repeated freeze–thawing of the extract. Keywords: decarboxylation, β-carboxyaspartic acid, Asa decarboxylase.