CLONING, SEQUENCING AND CHARACTERIZATION OF THE ALKALINE-PHOSPHATASE GENE (PHOD) FROM ZYMOMONAS-MOBILIS

The phoD gene encoding the membrane-bound alkaline phosphatase (ALPI) from Zymomonas mobilis CP4 was cloned and sequenced. Both the translat ed sequence and the properties of the recombinant enzyme were unusual. Z. mobilis ALPI was monomeric (M(r) 62926) and hydrolysed nucleotides more effectively than sugar phosphates. The translated sequence conta ined a single hydrophobic segment near the N-terminus which may serve as a membrane-anchor in Z. mobilis, although the recombinant enzyme wa s recovered in the cytoplasmic fraction of Escherichia coli. The predi cted amino acid sequence for ALPI did not align well with other ALPs o r other known genes. However, some similarity to E. coli ALP was noted in the metal-binding and phosphate-binding regions. Two other regions were identified with similarity to the active sites of pyruvate kinas e and mammalian 5'-nucleotide phosphodiesterase (also membrane-bound), respectively. It is likely that Z. mobilis phoD represents a new clas s of alkaline phosphatase genes which has not been described previousl y.