Diaminopimelic acid decarboyxlase in cells and extracts of Escherichia coli and Aerobacter aerogenes

Abstract

An enzyme which decarboxylates diaminopimelic acid was studied in single strains of E. coli and of A. aerogenes. Reaction products are L-lysine and CO2. The enzymic activity of the bacteria is unaffected by pH, composition or degree of aeration of the growth medium. In A. aerogenes, but not in E. coli, enzymic activity is unaffected by the phase of growth. The pH optimum is 7.2 for E. coli and 6.8 for A. aerogenes. Partially purified cell-free extracts of enzyme were obtained from A. aerogenes by fractional acetone extraction. The properties of the enzyme in such extracts were investigated. Pyridoxal phosphate is required for maximum activity; cyanide causes inhibition which is reversed by dialysis. The enzyme is inhibited strongly by Cu and other SH reactive inhibitors. Glutathione reverses para-chloromercuribenzoate inhibition. The enzyme is highly specific for natural diaminopimelic acid. Of those tested, no other naturally occurring amino acid or natural or synthetic homologue of diaminopimelic acid is decarboxylated. Decarboxylation of synthetic diaminopimelic is just half of that using the natural product.