Enhancing microperoxidase activity and selectivity: immobilization in metal-organic frameworks

Abstract

Microperoxidases 8 (MP8) and 11 (MP11) are heme-containing peptides obtained by the proteolytic digestion of Cytochrome c. They act as mini-enzymes that combine both peroxidase-like and Cytochrome P450-like activities that may be useful in the synthesis of fine chemicals or in the degradation of environmental pollutants. However, their use is limited by their instability in solution due to (i) the bleaching of the heme in the presence of an excess of H2O2, (ii) the decoordination of the distal histidine ligand of the iron under acidic conditions and, (iii) their tendency to aggregate in aqueous alkaline solutions, even at low concentrations. Additionally, both MP8 and MP11 show relatively low selectivity, due to the lack of control of the substrates by a specific catalytic pocket on the distal face of the heme. Both stability and selectivity issues can be effectively addressed by immobilization of microperoxidases in solid matrices, which can also lead to their possible recycling from the reaction medium. Considering their relatively small size, the pore inclusion of MPs into Metal-Organic Frameworks appeared to be more adequate compared to other immobilization methods that have been widely investigated for decades. The present minireview describes the catalytic activities of MP8 and MP11, their limitations, and various results describing their immobilization into MOFs which led to MP11- or MP8@MOF hybrid materials that display good activity in the oxidation of dyes and phenol derivatives, with remarkable recyclability due to the stabilization of the MPs inside the MOF cavities. An example of selective oxidation of dyes according to their charge by MP8@MOF hybrid materials is also highlighted.

Confining Natural/Mimetic Enzyme Cascade in an Amorphous Metal–Organic Framework for the Construction of Recyclable Biomaterials with Catalytic Activity

“…As shown in Figure C, GOx/MNP@aZIF-90 retained ∼70% of the initial overall activity for 12 days at 4 °C, while GOx/MNP@aZIF-90 retained ∼65% of the initial overall activity after 6 cycles of reuse (Figure D). The significant enhancement of stability might be attributed to the rigid structure of MOF, which restrains the enzyme structure from unfolding and avoids the leakage of enzymes through rigid restriction …”

Mimochrome, a metalloporphyrin‐based catalytic Swiss knife†

“…Consequently, these small molecules show dramatically increased peroxidase and peroxygenase activities compared to the parent, hexa-coordinated, Cyt c [157][158][159]. Though lacking a distal environment, they have been coupled to hosting moieties, like antibodies [160,161], silica channels [162], and metal-organic frameworks [163], in order to improve stability from auto-oxidation and directing substrate/product specificity. Moreover, through metal exchange technique, Bren's lab has shown that CoMP11 is a proficient hydrogen evolution catalyst in water, although with limited total turnover number (TON) [164].…”

Encapsulation of Microperoxidase-8 in MIL-101(Cr)-X Nanoparticles: Influence of Metal–Organic Framework Functionalization on Enzymatic Immobilization and Catalytic Activity

“…MP8 possesses dual catalytic activity (peroxidase-like and cytochrome P450-like activity) that allows the selective oxidation of organic molecules in water, including organosulfur compounds . However, the catalytic activity of MP8 is usually hampered by high concentrations of H 2 O 2 and acidic conditions. , We have recently demonstrated that MP8 encapsulation in nanoparticles of MIL-101­(Cr) enabled its protection and stabilization under these conditions . MIL-101­(Cr) has a high hierarchical, interconnected mesoporosity (cages of 2.9 and 3.4 nm) (Figure S1), compatible with the size of MP8 (<3.3 × 1.1 × 1.7 nm), and once the enzyme is immobilized, part of the porosity remains accessible for the diffusion of substrates.…”

“…19 However, the catalytic activity of MP8 is usually hampered by high concentrations of H 2 O 2 and acidic conditions. 20,21 We have recently demonstrated that MP8 encapsulation in nanoparticles of MIL-101(Cr) enabled its protection and stabilization under these conditions. 22 MIL-101(Cr) has a high hierarchical, interconnected mesoporosity (cages of 2.9 and 3.4 nm) (Figure S1), compatible with the size of MP8 (<3.3 × 1.1 × 1.7 nm), and once the enzyme is immobilized, part of the porosity remains accessible for the diffusion of substrates.…”