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Journal of Biological Sciences

Year: 2007 | Volume: 7 | Issue: 4 | Page No.: 607-613
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Authors

Thanaa H. Ali

Latifa A. Mohamed

Nadia H. Ali

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Research Article

Phytic Acid (Myo-inositol Hexakisphosphate) Phosphohydrolase from Streptomyces hygroscopicus NRRL B-1476

Thanaa H. Ali, Latifa A. Mohamed and Nadia H. Ali
Streptomyces hygroscopicus NRRL B-1476 could produce an extracellular constitutive phytase when grown on liquid Czapek Dox`s medium. Disappearance of phytase activity was observed on increasing orthophosphate concentration of the growth medium. Acetone-precipitated proteins of the growth medium showed optimum phytase activity at pH 6 and 50°C. The enzyme activity was retained when the enzyme preparation was exposed to 50°C for 30 min and was decreased and diminished on its exposure to higher degrees. Moderate activation of the enzyme action was observed on addition of Mg++ or Mn++ to the reaction mixture. Partial, considerable and complete inhibition were obtained in presence of Ag++, Ca++ or Hg++ ; F- and EDTA, respectively. Product inhibition was recorded on addition of orthophosphate to the reaction mixture. Orthophosphate inhibition was of the non competitive type and the Km and the Ki values were found to be 3.03 and 1.6H10G3 M, respectively. Streptomyces hygroscopicus phytase exhibited a broad affinity for different phosphorylated compounds and the highest relative rate of hydrolysis was found with ATP.
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