The role of PTP-like phytases in ruminal phytate digestion

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Phytate is the principal form of phosphorus stored in grains and, as such is the major source of phosphorus in grain-based diets used in intensive livestock production. Phytate-phosphorus is indigestible to non-ruminant livestock (e.g., swine, poultry) and excreted in the feces. Release of phytate-phosphorus following application of manure to arable lands is a significant source of pollution and has contributed to eutrophication of surface waters in areas of the world with high densities of non-ruminant livestock. The annual amount of phosphorus excreted globally by non-ruminants exceeds 800,000,000 kg and represents to producers an annual worldwide loss of greater than $1 billion dollars. One solution to the inability of non-ruminants to use dietary phytate is the amendment of diets with phytases. Phytases release phytate-phosphorus, thereby making it available to non-ruminant animals. Interestingly, microbial activities in the rumen enable ruminant animals (e.g., cattle, sheep) to use phytate-phosphorus. The overall objective of my research is to determine how ruminal anaerobic bacteria degrade phytate. We have identified a number of high phytase producing anaerobic bacteria in the rumen, including Selenomonads and relatives in cluster IX. I propose to use techniques in biochemistry and molecular biology to study the genetics and biochemistry of phytate degradation by Selenomonads and related anaerobic bacteria. My research group has recently described a novel family of phytases produced by these rumen bacteria. We have characterized 6 enzymes that are distantly related to Protein Tyrosine Phosphatases, an important class of enzymes involved in regulating fundamental cellular processes. We are currently determining the structure, mode of action and distribution of this new family of phytase in an attempt to gain insights into phytate degradation and its role in phosphorus cycling in the rumen. This research will provide new solutions and tools to deal effectively with a growing pollution problem.