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The enzyme 5-phytase (EC 3.1.3.72) catalyzes the reaction

myo-inositol hexakisphosphate + H₂O = 1L-myo-inositol 1,2,3,4,6-pentakisphosphate + phosphate

myo-Inositol hexakisphosphate is also known as phytic acid.

These enzymes belongs to the family of hydrolases, specifically those acting on phosphoric monoester bonds. The systematic name of this enzyme class is myo-inositol-hexakisphosphate 5-phosphohydrolase.

Prevalence

Of the hundreds of phytase enzymes that have been characterized in the literature, only two have been characterized as 5-phytases. A histidine acid phosphatases purified from lily pollen and a protein tyrosine phosphatase-like phytase from Selenomonas ruminantium subsp. lactilytica were both found to have specificity for the 5-phosphate position of myo-inositol hexakisphosphate.

Structural studies

As of late 2007, only the phytase purified from lily pollen had its structure solved, with PDB accession codes 1U24, 1U25, 1U26, 2B4O, 2B4P, and 2B4U.

See also

• 3-phytase (1-phytase)
• 4-phytase (6-phytase)
• Protein tyrosine phosphatase

References

1. ^ Barrientos L, Scott JJ, Murthy PP (1994). "Specificity of hydrolysis of phytic acid by alkaline phytase from lily pollen". Plant Physiology. 106 (4): 1489–1495. doi:10.1104/pp.106.4.1489. PMC 159689. PMID 7846160.
2. ^ Puhl A, Greiner R, Selinger LB (2008). "A protein tyrosine phosphatase-like inositol polyphosphatase from Selenomonas ruminantium subsp. lactilytica has specificity for the 5-phosphate of myo-inositol hexakisphosphate". The International Journal of Biochemistry & Cell Biology. 40 (10): 2053–2064. doi:10.1016/j.biocel.2008.02.003. PMID 18358762.

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