Department of Chemistry, Umeå University, SE-901 87 Umeå, Sweden.
Environ Sci Technol. 2012 Jan 3;46(1):285-91. doi: 10.1021/es2028422. Epub 2011 Dec 12.
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.
磷酸酯构成了环境中总磷供应的相当大一部分，因此在全球磷循环中起着重要作用。这些酯的酶促水解产生正磷酸盐通常是植物和微生物吸收磷之前的必要反应。通常，假定吸附到环境颗粒上会限制这个过程。然而，我们在这里表明，酸性磷酸酶（AcPase）在针铁矿上吸附的葡萄糖-1-磷酸（G1P）的酶促水解速率可以与在水溶液中的速率相同。表面过程将碳释放到溶液中，而正磷酸盐仍然吸附在针铁矿上。这种水解反应是严格受界面性质控制的界面过程。高表面浓度的底物介导了 AcPase 的催化活性层的形成，尽管吸附可能会降低酶的催化效率，但这种降低几乎被酶和底物在矿物表面浓缩的事实所平衡。我们的结果表明，具有适当表面性质的矿物表面可以非常有效地浓缩底物和酶，从而创造出具有高酶活性的微观化学环境。因此，土壤和水生环境中吸附较强的分子也可能受到细胞外酶的生物降解。
