http://www.biogeosciences-discuss.net/12/5055/2015/bgd-12-5055-2015.html

C. v. Sperber^1,2, F. Tamburini¹, B. Brunner³, S. M. Bernasconi⁴, and E. Frossard¹

¹Institute of Agricultural Sciences, ETH Zurich, Eschikon 33, 8315 Lindau, Switzerland
²Department of Biology, Stanford University, 473 Via Ortega, Y2E2 Building, Stanford, California 94305–5020, USA
³Department of Geosciences, University of Texas at El Paso, 500 W. University Ave, El Paso, TX 79902, USA
⁴Geological Institute, ETH Zurich, Sonnegstrasse 5, 8092 Zurich, Switzerland

von Sperber and coauthors investigated the fractionation of oxygen from water into phosphate during the hydrolysis of phytic acid by two phytases. They report an inverse isotopic fractionation (ϵ ∼ 6 to 10‰), which is similar to acid phosphatase from potato (ϵ ∼ 7‰), and discuss differences in the fractionation values across substrates (AMP and glucose phosphate). The authors suggest that the substrate-dependency of the fractionation could be related to differences in the inital δ¹⁸O-values in the monoester bonds for the different organic P compounds tested.

This work makes a significant contribution to our understanding of organic P cycling and the use of stable isotopes of phosphate to track the dynamics of phosphorus in the environment.