Expanding the Scope of Polyoxometalates as Artificial Proteases towards Hydrolysis of Insoluble Proteins

• Published in: Chemistry : a European journal 2022-02, Vol.28 (8), p.e202104224-n/a
• Main Authors: Savić, Nada D., Salazar Marcano, David E., Parac‐Vogt, Tatjana N.
• Format: Article
• Language: English
• Subjects: Anions; Biological activity; catalysis; Catalysts; Chemistry; Hydrolysis; insoluble proteins; Light scattering; Molecular interactions; Peptide Hydrolases; Photon correlation spectroscopy; Pollutants; Polyelectrolytes; polyoxometalates; Polyoxometallates; Proteins; Proteomics; Selectivity; Sodium dodecyl sulfate; Sodium lauryl sulfate; Superstructures; Surface-Active Agents; Surfactants; Tungsten Compounds; Zein; Zirconium
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.202104224

Despite the enormous importance of insoluble proteins in biological processes, their structural investigation remains a challenging task. The development of artificial enzyme‐like catalysts would greatly facilitate the elucidation of their structure since currently used enzymes in proteomics largely lose activity in the presence of surfactants, which are necessary to solubilize insoluble proteins. In this study, the hydrolysis of a fully insoluble protein by polyoxometalate complexes as artificial proteases in surfactant solutions is reported for the first time. The hydrolysis of zein as a model protein was investigated in the presence of Zr(IV) and Hf(IV) substituted Keggin‐type polyoxometalates (POMs), (Et2NH2)10[M(α‐PW11O39)2] (M = Zr or Hf), and different concentrations of the anionic surfactant sodium dodecyl sulfate (SDS). Selective hydrolysis of the protein upon incubation with the catalyst was observed, and the results indicate that the hydrolytic selectivity and activity of the POM catalysts strongly depends on the concentration of surfactant. The molecular interactions between the POM catalyst and zein in the presence of SDS were explored using a combination of spectroscopic techniques which indicated competitive binding between POM and SDS towards the protein. Furthermore, the formation of micellar superstructures in ternary POM/surfactant/protein solutions has been confirmed by conductivity and Dynamic Light Scattering measurements. The development of artificial proteases able to hydrolyze insoluble proteins in the presence of surfactants remains essential for their structural characterization. Therefore, we report for the first time metal‐substituted Keggin‐type polyoxometalate complexes (M‐K 1 : 2 where M = Zr(IV) or Hf(IV)) as catalysts for the hydrolysis of a fully insoluble protein, zein, in the presence of sodium dodecyl sulfate (SDS) via a competitive binding mechanism, which results in a dependence of the hydrolysis on the surfactant concentration.