Hydrolysis of transferrin promoted by a cerium(IV)-Keggin polyoxometalate

• Published in: Polyhedron Vol. 170; pp. 570 - 575
• Main Authors: Moons, Jens, Van Rompuy, Laura S., Rodriguez, Alvaro, Abdelhameed, Shorok A.M., Simons, Wouter, Parac-Vogt, Tatjana N.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.09.2019
• Subjects: Cerium; Hydrolysis; Polyoxometalate; Protein; Transferrin; Hydrolysis; Polyoxometalate; Cerium; Transferrin; Protein
• ISSN: 0277-5387
• DOI: 10.1016/j.poly.2019.06.010

Selective hydrolysis of Transferrin (Tf), a glycoprotein consisting of 679 amino acids and three glycan chains has been achieved in the presence of Ce(IV)-substituted Keggin polyoxometalate [CeIV(α-PW11O39)2]10− under physiological conditions (pH = 7.4 and at 37 °C), demonstrating the potential of polyoxometalates to act as artificial proteases. [Display omitted] Hydrolysis of Transferin (Tf), a glycoprotein consisting of 679 amino acids and three glycan chains, has been examined in the presence of Ce(IV)-substituted Keggin polyoxometalate [CeIV(α-PW11O39)2]10− (Ce-K POM). Incubation at pH = 7.4 and at 37 °C resulted in selective fragmentation of the Tf after 24 h, which was followed by sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS–PAGE). After 5 days of incubation nearly 90% of Tf was hydrolyzed, giving 9 fragments with molecular weight (Mw) in the range between 13.7 and 69.5 kDa. Under the same conditions, the sample of Tf which did not contain the Ce-K POM, showed only 7% of background hydrolysis. The interactions between Ce-K and Tf were studied by tryptophan fluorescence, circular dichroism (CD) and 31P Nuclear magnetic resonance (NMR) spectroscopy. The association constant (Ka) for the interaction was calculated to be 3.2 × 104 M−1 from tryptophan quenching studies. CD spectroscopy revealed that binding of Ce-K to Tf resulted in significant secondary structure changes, mainly affecting the alpha-helical content of the protein. 31P NMR spectroscopy showed that in the presence of the Tf partial reduction of Ce(IV) to Ce(III) occurred, which did not affect the overall structure of the Keggin POM.