Shigella apyrase--a novel variant of bacterial acid phosphatases?

A virulence-associated ATP diphosphohydrolase activity in the periplasm of Shigella, identified as apyrase, was found to be markedly similar to bacterial non-specific acid phosphatases in primary structure. When the Shigella apyrase sequence was threaded in to the recently published 3D structure of the highly similar (73%) Escherichia blattae acid phosphatase it was found to have a highly overlapping 3D structure. Our analysis, which included assays for phosphatase, haloperoxidase and catalase activities, led us to hypothesize that Shigella apyrase might belong to a new class of pyrophosphatase originating as one more variant in the family of bacterial non-specific acid phosphatases. It revealed interesting structure-function relationships and probable roles relevant to pathogenesis.