Characterisation of a soil MINPP phytase with remarkable long-term stability and activity from Acinetobacter sp.

Rix, Gregory D., Sprigg, Colleen, Whitfield, Hayley, Hemmings, Andrew M. ORCID: https://orcid.org/0000-0003-3053-3134, Todd, Jonathan D. and Brearley, Charles A. ORCID: https://orcid.org/0000-0001-6179-9109 (2022) Characterisation of a soil MINPP phytase with remarkable long-term stability and activity from Acinetobacter sp. PLoS One, 17 (8). ISSN 1932-6203

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Abstract

Phylogenetic analysis, homology modelling and biochemical methods have been employed to characterize a phytase from a Gram-negative soil bacterium. Acinetobacter sp. AC1-2 phytase belongs to clade 2 of the histidine (acid) phytases, to the Multiple Inositol Polyphosphate Phosphatase (MINPP) subclass. The enzyme was extraordinarily stable in solution both at room temperature and 4 °C, retaining near 100% activity over 755 days. It showed a broad pH activity profile from 2-8.5 with maxima at 3, 4.5-5 and 6. The enzyme showed Michaelis-Menten kinetics and substrate inhibition (Vmax, Km, and Ki, 228 U/mg, 0.65 mM and 2.23 mM, respectively). Homology modelling using the crystal structure of a homologous MINPP from a human gut commensal bacterium indicated the presence of a potentially stabilising polypeptide loop (a U-loop) straddling the active site. By employ of the enantiospecificity of Arabidopsis inositol tris/tetrakisphosphate kinase 1 for inositol pentakisphosphates, we show AC1-2 MINPP to possess D6-phytase activity, which allowed modelling of active site specificity pockets for InsP6 substrate. While phytase gene transcription was unaltered in rich media, it was repressed in minimal media with phytic acid and orthophosphate as phosphate sources. The results of this study reveal AC1-2 MINPP to possess desirable attributes relevant to biotechnological use.

Item Type: Article
Additional Information: Funding: GDR was funded by Natural Environment Research Council (NERC) PhD studentships (NERC Doctoral Training Programme grant NE/L002582/1) with support from AB Vista. HW was funded by Natural Environment Research Council (NERC grant: NE/W000350/1). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Faculty \ School: Faculty of Science > School of Biological Sciences
Faculty of Science > School of Chemistry
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Depositing User: LivePure Connector
Date Deposited: 24 Aug 2022 15:30
Last Modified: 21 Oct 2022 01:34
URI: https://ueaeprints.uea.ac.uk/id/eprint/87607
DOI: 10.1371/journal.pone.0272015

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