title: Poly(N-vinylpyrrolidone)-poly(dimethylsiloxane)-based polymersome nanoreactors for laccase-catalyzed biotransformations.
abstract: Laccases (Lac) are oxidizing enzymes with a broad range of applications, for example, in soil remediation, as bleaching agent in the textile industry, and for cosmetics. Protecting the enzyme against degradation and inhibition is of great importance for many of these applications. Polymer vesicles (polymersomes) from poly(N-vinylpyrrolidone)-block-poly(dimethylsiloxane)-block-poly(N-vinylpyrrolidone) (PNVP-b-PDMS-b-PNVP) triblock copolymers were prepared and investigated as intrinsically semipermeable nanoreactors for Lac. The block copolymers allow oxygen to enter and reactive oxygen species (ROS) to leave the polymersomes. EPR spectroscopy proved that Lac can generate ROS. They could diffuse out of the polymersome and oxidize an aromatic substrate outside the vesicles. Michaelis-Menten constants Km between 60 and 143 μM and turn over numbers kcat of 0.11 to 0.18 s(-1) were determined for Lac in the nanoreactors. The molecular weight and the PDMS-to-PNVP ratio of the block copolymers influenced these apparent Michaelis-Menten parameters. Encapsulation of Lac in the polymersomes significantly protected the enzyme against enzymatic degradation and against small inhibitors: proteinase K caused 90% less degradation and the inhibitor sodium azide did not affect the enzyme's activity. Therefore, these polymer nanoreactors are an effective means to stabilize laccase.
authors.affiliation: Department of Chemistry, University of Basel , Klingelbergstrasse 80, 4056 Basel, Switzerland.
authors.forename: Mariana
authors.initials: M
authors.lastname: Spulber
authors.forename: Patric
authors.initials: P
authors.lastname: Baumann
authors.forename: Sina S
authors.initials: SS
authors.lastname: Saxer
authors.forename: Uwe
authors.initials: U
authors.lastname: Pieles
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Meier
authors.forename: Nico
authors.initials: N
authors.lastname: Bruns
mesh_terms: D004578:Electron Spin Resonance Spectroscopy; D019286:Endopeptidase K / Q000378:metabolism; D004795:Enzyme Stability; D057927:Hydrophobic and Hydrophilic Interactions; D042845:Laccase / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism*; D008970:Molecular Weight; D036103:Nanotechnology / Q000379:methods*; D010100:Oxygen / Q000378:metabolism; D011205:Povidone / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry; D017382:Reactive Oxygen Species / Q000378:metabolism; D012833:Siloxanes / Q000138:chemical synthesis / Q000737:chemistry*; D019810:Sodium Azide / Q000378:metabolism / Q000494:pharmacology
chemical_list: D017382:Reactive Oxygen Species; D012833:Siloxanes; D019810:Sodium Azide; D042845:Laccase; D019286:Endopeptidase K; D011205:Povidone; D010100:Oxygen