Article Abstract:
Research was conducted to examine the thermostabilities of three acid phosphatases and a pH 2.5 acid phosphatase through the measurement of circular dichroism, activity and fluorescence and through feed pelleting experiments. Aspergillus fumigatus phytase, A. niger phytase and A. niger pH 2.5 acid phosphatase were taken from various molds, cloned and overexpressed. Results indicate that A. fumigatus phytase and A. niger T213 phytase were not thermostable but had the ability to refold completely. A. niger T213 pH 2.5 acid phosphatase showed higher intrinsic thermostability.
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Article Abstract:
The phytase-encoding gene (phyA) was cloned from Aspergillus fumigatus and overexpressed in Aspergillus niger to determine the effects of hydrogen-ion concentration (pH) and heat stability on the activity of the phosphatase. Characterization of the histidine acid phosphatase from phyA-expressing Aspergillus niger indicated the ability of the enzyme to withstand temperatures that were normally reached during the feed-pelleting process. Furthermore, the Aspergillus fumigatus phyA enzyme catalyzed phytic acid hydrolysis over a broad pH range.
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Article Abstract:
DNA library screening and site-directed mutagenesis were done to isolate and characterize the genes encoding phytases from two filamentous fungi, Aspergillus terreus strain 9A-a and Myceliophthora thermophila. Enzyme studies revealed that both proteins prefer phytic acid as substrate. They also demonstrated a drastically different pH optima. It was also confirmed that the two phytases belong to a novel subclass of histidine acid phosphatase family.
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