Biochemical characterisation of extracellular phytase (myo-inositol hexakisphosphate phosphohydrolase) from a hyper-producing strain of Aspergillus niger van Teighem.

Vats, Purva and Banerjee, U C (2005) Biochemical characterisation of extracellular phytase (myo-inositol hexakisphosphate phosphohydrolase) from a hyper-producing strain of Aspergillus niger van Teighem. Journal of industrial microbiology & biotechnology, 32 (4). pp. 141-7. ISSN 1367-5435

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Abstract

Aspergillus niger van Teighem, isolated in our laboratory from samples of rotten wood logs, produced extracellular phytase having a high specific activity of 22,592 units (mg protein)-1 . The enzyme was purified to near homogeneity using ion-exchange and gel-filtration chromatography. The molecular properties of the purified enzyme suggested the native phytase to be oligomeric, with a molecular weight of 353 kDa, the monomer being 66 kDa. The purified enzyme exhibited maximum activity at pH 2.5 and 52-55 degrees C. The enzyme retained 97% activity after a 24-h incubation at 55 degrees C in the presence of 10 mM glycine, while 87% activity was retained when no thermoprotectant was added. Phytase activity was not affected by most metal ions, inhibitors and organic solvents. Non-ionic and cationic detergents (0.1-5%) stabilise the enzyme, while the anionic detergent (SDS), even at a 0.1% level, severely inhibited enzyme activity. The chaotropic agents guanidinium hydrochloride, urea, and potassium iodide (0.5-8 M), significantly affected phytase activity. The maximum hydrolysis rate (Vmax) and apparent Michaelis-Menten constant (Km) were 1,074 IU/mL and 606 microM, respectively, with a catalytic turnover number of 3x10(5) s-1 and catalytic efficiency of 3.69x10(8) M-1 s-1.

Item Type:	Article
Additional Information:	Copyright of this article belongs to Springer Science.
Uncontrolled Keywords:	Aspergillus niger - Phytases - Acid-phosphatases
Subjects:	Q Science > QR Microbiology
Depositing User:	Dr. K.P.S.Sengar
Date Deposited:	08 Jan 2012 05:41
Last Modified:	08 Jan 2012 05:41
URI:	http://crdd.osdd.net/open/id/eprint/182

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