A novel purple acid phytase from an earthworm cast bacterium

Phytases are a diverse group of enzymes initiating the dephosphorylation of phytate. Phytate is considered as an anti-nutritional compound because of its capability to chelate nutrients such as Fe²⁺ , Zn²⁺ , Mg²⁺ , and Ca²⁺ . In this study, several bacterial isolates obtained from earthworm casts were evaluated for their phytate degrading capability. Enzymatic properties and the sequence of the corresponding phytase-encoding gene of the selected isolate were determined.

The phytase exhibited its highest activity at pH 4.0 and was stable from pH 3 up to pH 9. The temperature optimum was determined to be 65 °C. The strongest inhibitors of enzymatic activity were identified as vanadate, Cu²⁺ , and Zn²⁺ . High-performance ion chromatography analysis of enzymatic phytate dephosphorylation revealed that the first dephosphorylation product was d/l-myo-inositol(1,2,3,4,5)pentakisphosphate.

Owing to its enzymatic properties, such as tolerance to tartrate and the presence of the consensus motifs PDTVY, GNHE, DLG, VLFH, and GHDH, this phytase could be classified as a purple acid phytase. To the best of our knowledge, this is the first report describing a bacterial purple acid phytase. © 2017 Society of Chemical Industry.