Identification of the gene appA for the acid phosphatase (pH optimum 2.5) of Escherichia coli.

A strain of Escherichia coli exhibiting reduced activity of the periplasmic enzyme acid phosphoanhydride phosphohydrolase (pH 2.5 acid phosphatase) was isolated. The mutation designated appA1 was located at 22.5 min on the E. coli genetic map. Acid phosphatase purified from an appA- transductant showed less than ten percent of the specific activity of an isogenic appA+ strain. The mutant enzyme was highly thermolabile and its Km for paranitrophenyl phosphate was increased about 20-fold. The mutant protein cross-reacted with antibody to the wild-type enzyme and had the same molecular weight and concentration in extracts as the wild-type enzyme. These findings strongly suggest that appA is the structural gene of the acid phosphatase.