pH dependent phosphate hydrolysis by a lanthanide EF-hand peptide

A 20-mer peptide comprising an EF-hand calcium-binding sequence was shown to bind Eu(III) ions and promote phosphate ester cleavage in a pH dependent manner. The hydrolysis rate of bisnitrophenyl phosphate (BNPP) was followed over a 6.9–9.0 pH range, and the rate increases sharply at pH 8.2. This rate increase, which may correlate to the pKa of an inner sphere water of an Eu-EF-hand motif, is discussed in the context of coordinate water pKa values for a variety of small molecule Eu complexes.