phosphatase PTEN, and significant sequence homology to the PTP domain of a type III-secreted virulence protein from Pseudomonas syringae (HopPtoD2). Biochemical characteristics Substrate specificity Most phytases show a broad substrate specificity, having the ability to hydrolyze many phosphorylated compounds that are not structurally similar to phytic acid such as ADP, ATP, phenyl phosphate, fructose 1,6-bisphosphate, glucose 6-phosphate, glycerophosphate and 3-phosphoglycerate. Only a few phytases have been described as highly specific for phytic acid, such as phytases from Bacillus sp., Aspergillus sp., E. coli and those phytases belonging to the class of PTP-like phytases Pathways of phytic acid dephosphorylation Phytic acid has six phosphate groups that may be released by phytases at different rates and in different order. Phytases hydrolyze phosphates from phytic acid in a stepwise manner, yielding products that again become substrates for further hydrolysis. Most phytases are able to cleave five of the six phosphate groups from phytic acid. Phytases have been grouped based on the first phosphate position of phytic acid that is hydrolyzed. The Enzyme Nomenclature Committee of the International Union of Biochemistry recognizes three types of phytases based on the position of the first phosphate hydrolyzed, those are 3-phytase (), 4-phytase (), and 5-phytase (). To date, most of the known phytases are 3-phytases or 4-phytases, only a HAP purified from lily pollen and a PTP-like phytase from Selenomonas ruminantium subsp. lactilytica have been determined to be 5-phytases. Biological relevance Phytic acid and its metabolites have several important roles in seeds and grains, most notably, phytic acid functions as a phosphorus store, as an energy store, as a source of cations and as a source of myo-inositol (a cell wall precursor). Phytic acid is the principal storage forms of phosphorus in plant seeds and the major source of phosphorus in the grain-based diets used in intensive livestock operations. The organic phosphate found in phytic acid is largely unavailable to the animals that consume it, but the inorganic phosphate that phytases release can be easily absorbed. Ruminant animals can use phytic acid as a source of phosphorus because the bacteria that inhabit their gut are well characterized producers of many types of phytases. However, monogastric animals do not carry bacteria that produce phytase, thus, these animals cannot use phytic acid as a major source of phosphorus and it is excreted in the feces. However, human—especially vegetarians and vegans due to increased gut microbiome adaptation—can have microbes