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Appl Environ Microbiol. 1998 Nov;64(11):4423-7.

Molecular characterization and expression of a phytase gene from the thermophilic fungus Thermomyces lanuginosus.

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  • 1Novo Nordisk Biotech, Davis, California 95616-4880, USA.


The phyA gene encoding an extracellular phytase from the thermophilic fungus Thermomyces lanuginosus was cloned and heterologously expressed, and the recombinant gene product was biochemically characterized. The phyA gene encodes a primary translation product (PhyA) of 475 amino acids (aa) which includes a putative signal peptide (23 aa) and propeptide (10 aa). The deduced amino acid sequence of PhyA has limited sequence identity (ca. 47%) with Aspergillus niger phytase. The phyA gene was inserted into an expression vector under transcriptional control of the Fusarium oxysporum trypsin gene promoter and used to transform a Fusarium venenatum recipient strain. The secreted recombinant phytase protein was enzymatically active between pHs 3 and 7.5, with a specific activity of 110 micromol of inorganic phosphate released per min per mg of protein at pH 6 and 37 degrees C. The Thermomyces phytase retained activity at assay temperatures up to 75 degrees C and demonstrated superior catalytic efficiency to any known fungal phytase at 65 degrees C (the temperature optimum). Comparison of this new Thermomyces catalyst with the well-known Aspergillus niger phytase reveals other favorable properties for the enzyme derived from the thermophilic gene donor, including catalytic activity over an expanded pH range.

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