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Avian multiple inositol polyphosphate phosphatase is an active phytase that can be engineered to help ameliorate the planet's "phosphate crisis".

ABSTRACT: Contemporary phytase research is primarily concerned with ameliorating the problem of inadequate digestion of inositol hexakisphosphate (phytate; InsP6) in monogastric farm animal feed, so as to reduce the pollution that results from the high phosphate content of the manure. In the current study we pursue a new, safe and cost-effective solution. We demonstrate that the rate of hydrolysis of InsP6 by recombinant avian MINPP (0.7 micromol/mg protein/min) defines it as by far the most active phytase found to date in any animal cell (the corresponding activity of recombinant mammalian MINPP is only 0.006 micromol/mg protein/min). Although avian MINPP has less than 20% sequence identity with microbial phytases, we create a homology model of MINPP in which it is predicted that the structure of the phytase active site is well-conserved. This model is validated by site-directed mutagenesis and by use of a substrate analogue, scyllo-InsP6, which we demonstrate is only a weak MINPP substrate. In a model chicken cell line, we overexpressed a mutant form of MINPP that is secretion-competent. This version of the enzyme was actively secreted without affecting either cell viability or the cellular levels of any inositol phosphates. Our studies offer a genetic strategy for greatly improving dietary InsP6 digestion in poultry.

SUBMITTER: Cho J

PROVIDER: S-EPMC1892222 | biostudies-literature | 2006 Nov

REPOSITORIES: biostudies-literature

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Avian multiple inositol polyphosphate phosphatase is an active phytase that can be engineered to help ameliorate the planet's "phosphate crisis".

Cho Jaiesoon J Choi Kuicheon K Darden Thomas T Reynolds Paul R PR Petitte James N JN Shears Stephen B SB

Journal of biotechnology 20060606 2

Contemporary phytase research is primarily concerned with ameliorating the problem of inadequate digestion of inositol hexakisphosphate (phytate; InsP6) in monogastric farm animal feed, so as to reduce the pollution that results from the high phosphate content of the manure. In the current study we pursue a new, safe and cost-effective solution. We demonstrate that the rate of hydrolysis of InsP6 by recombinant avian MINPP (0.7 micromol/mg protein/min) defines it as by far the most active phytas ...[more]

PMID: 16759730

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Project description:Phytases, enzymes that degrade phytate present in feedstuffs, are widely added to the diets of monogastric animals. Many studies have correlated phytase addition with improved animal productivity and a subset of these have sought to correlate animal performance with phytase-mediated generation of inositol phosphates in different parts of the gastro-intestinal tract or with release of inositol or of phosphate, the absorbable products of phytate degradation. Remarkably, the effect of dietary phytase on tissue inositol phosphates has not been studied. The objective of this study was to determine effect of phytase supplementation on liver and kidney myo-inositol and myo-inositol phosphates in broiler chickens. For this, methods were developed to measure inositol phosphates in chicken tissues. The study comprised wheat/soy-based diets containing one of three levels of phytase (0, 500 and 6,000 FTU/kg of modified E. coli 6-phytase). Diets were provided to broilers for 21 D and on day 21 digesta were collected from the gizzard and ileum. Liver and kidney tissue were harvested. Myo-inositol and inositol phosphates were measured in diet, digesta, liver and kidney. Gizzard and ileal content inositol was increased progressively, and total inositol phosphates reduced progressively, by phytase supplementation. The predominant higher inositol phosphates detected in tissues, D-and/or L-Ins(3,4,5,6)P4 and Ins(1,3,4,5,6)P5, differed from those (D-and/or L-Ins(1,2,3,4)P4, D-and/or L-Ins(1,2,5,6)P4, Ins(1,2,3,4,6)P5, D-and/or L-Ins(1,2,3,4,5)P5 and D-and/or L-Ins(1,2,4,5,6)P5) generated from phytate (InsP6) degradation by E. coli 6-phytase or endogenous feed phytase, suggesting tissue inositol phosphates are not the result of direct absorption. Kidney inositol phosphates were reduced progressively by phytase supplementation. These data suggest that tissue inositol phosphate concentrations can be influenced by dietary phytase inclusion rate and that such effects are tissue specific, though the consequences for physiology of such changes have yet to be elucidated.

Dataset Information

Avian multiple inositol polyphosphate phosphatase is an active phytase that can be engineered to help ameliorate the planet's "phosphate crisis".

Publications

Avian multiple inositol polyphosphate phosphatase is an active phytase that can be engineered to help ameliorate the planet's "phosphate crisis".

Similar Datasets

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