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Enzymatic hydrolysis of organic phosphates adsorbed on mineral surfaces
Umeå University, Faculty of Science and Technology, Department of Chemistry.
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
Pacific Northwest National Laboratory.
Umeå University, Faculty of Science and Technology, Department of Chemistry.
2012 (English)In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 46, 285-291 p.Article in journal (Refereed) Published
Abstract [en]

Esters of phosphoric acid constitute a sizable fraction of the total phosphorus supply in the environment and thus play an important role in the global phosphorus cycle. Enzymatic hydrolysis of these esters to produce orthophosphate is often a required reaction preceding phosphorus uptake by plants and microorganisms. Generally, adsorption to environmental particles is assumed to limit this process. Here we show, however, that the rate of enzymatic hydrolysis of glucose-1-phosphate (G1P) adsorbed on goethite by acid phosphatase (AcPase) can be of the same order of magnitude as in aqueous solution. The surface process releases carbon to the solution whereas orthophosphate remains adsorbed on goethite. This hydrolysis reaction is strictly an interfacial process governed by the properties of the interface. A high surface concentration of substrate mediates the formation of a catalytically active layer of AcPase, and although adsorption likely reduces the catalytic efficiency of the enzyme, this reduction is almost balanced by the fact that enzyme and substrate are concentrated at the mineral surfaces. Our results suggest that mineral surfaces with appropriate surface properties can be very effective in concentrating substrates and enzymes thereby creating microchemical environments of high enzymatic activity. Hence, also strongly adsorbed molecules in soils and aquatic environments may be subjected to biodegradation by extracellular enzymes.

Place, publisher, year, edition, pages
2012. Vol. 46, 285-291 p.
National Category
Other Basic Medicine
Identifiers
URN: urn:nbn:se:umu:diva-46541DOI: 10.1021/es2028422OAI: oai:DiVA.org:umu-46541DiVA: diva2:438796
Available from: 2011-09-05 Created: 2011-09-05 Last updated: 2017-12-08Bibliographically approved
In thesis
1. Surface reactions on mineral particles controlling the hydrolysis of glucose phosphates
Open this publication in new window or tab >>Surface reactions on mineral particles controlling the hydrolysis of glucose phosphates
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Phosphorus (P) is an essential nutrient. A significant amount of soil P may be in the form of organophosphates. Due to the size of these compounds, hydrolysis is often required before P can be assimilated by organisms. Hydrolysis may be mediated by mineral surfaces, or catalyzed by extra cellular enzymes. Since both organophosphates and enzymes have a strong affinity for environmental particles, a study of the hydrolysis of organophosphates must focus on reactions at the water/particle interface. This thesis is a summary of four papers, discussing the adsorption, desorption, and abiotic and enzymatic hydrolysis of glucose-1-phosphate (G1P) and glucose-6-phosphate (G6P) in aqueous goethite suspensions. A new technique for simultaneous infrared and potentiometric titrations (SIPT) allowed in-situ measurements of the interfacial reactions. It was found that glucose phosphates form pH-dependent inner sphere complexes on goethite, which coordinate in a monodentate fashion, and are stabilized by hydrogen bonding. Desorption involves a change in speciation of the surface complexes, illustrating the difficulty in determining desorption rates for individual complexes. The surface mediated hydrolysis is primarily base catalyzed for G1P, and acid catalyzed for G6P. The difference is partly due to electronic factors, and partly to differences in glucose group/goethite interactions. Considerably more extensive is the hydrolysis catalyzed by an acid phosphatase (AcPase). The rate of the enzymatic hydrolysis are strongly dependent on the glucose phosphate surface coverage, showing that surface properties affect the adsorption mode of enzymes, and thus their catalytic activity. In solution, AcPase showed a greater specificity towards G6P, but this specificity was partly lost after adsorption onto goethite.

Place, publisher, year, edition, pages
Umeå: Kemiska institutionen, Umeå universitet, 2011
National Category
Other Basic Medicine
Identifiers
urn:nbn:se:umu:diva-46578 (URN)978-91-7459-270-2 (ISBN)
Public defence
2011-09-30, KBC-huset, KB3A9, Umeå universitet, Umeå, 10:00 (English)
Opponent
Supervisors
Available from: 2011-09-09 Created: 2011-09-06 Last updated: 2011-09-06Bibliographically approved

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