title: Functionalized graphene oxide in enzyme engineering: a selective modulator for enzyme activity and thermostability.
abstract: The understanding of interactions between nanomaterials and biomolecules is of fundamental importance to the area of nanobiotechnology. Graphene and its derivative, graphene oxide (GO), are two-dimensional (2-D) nanomaterials with interesting physical and chemical properties and have been widely explored in various directions of biomedicine in recent years. However, how functionalized GO interacts with bioactive proteins such as enzymes and its potential in enzyme engineering have been rarely explored. In this study, we carefully investigated the interactions between serine proteases and GO functionalized with different amine-terminated polyethylene glycol (PEG). Three well-characterized serine proteases (trypsin, chymotrypsin, and proteinase K) with important biomedical and industrial applications were analyzed. It is found that these PEGylated GOs could selectively improve trypsin activity and thermostability (60-70% retained activity at 80 °C), while exhibiting barely any effect on chymotrypsin or proteinase K. Detailed investigation illustrates that the PEGylated GO-induced acceleration is substrate-dependent, affecting only phosphorylated protein substrates, and that at least up to 43-fold increase could be achieved depending on the substrate concentration. This unique phenomenon, interestingly, is found to be attributed to both the terminal amino groups on polymer coatings and the 2-D structure of GO. Moreover, an enzyme-based bioassay system is further demonstrated utilizing our GO-based enzyme modulator in a proof-of-concept experiment. To our best knowledge, this work is the first success of using functionalized GO as an efficient enzyme positive modulator with great selectivity, exhibiting a novel potential of GO, when appropriately functionalized, in enzyme engineering as well as enzyme-based biosensing and detection.
authors.affiliation: Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Soochow University, Suzhou, Jiangsu 215123, China.
authors.forename: Liling
authors.initials: L
authors.lastname: Jin
authors.forename: Kai
authors.initials: K
authors.lastname: Yang
authors.forename: Kai
authors.initials: K
authors.lastname: Yao
authors.forename: Shuai
authors.initials: S
authors.lastname: Zhang
authors.forename: Huiquan
authors.initials: H
authors.lastname: Tao
authors.forename: Shuit-Tong
authors.initials: ST
authors.lastname: Lee
authors.forename: Zhuang
authors.initials: Z
authors.lastname: Liu
authors.forename: Rui
authors.initials: R
authors.lastname: Peng
mesh_terms: D004789:Enzyme Activation; D004795:Enzyme Stability; D006108:Graphite / Q000737:chemistry*; D008422:Materials Testing; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure*; D010087:Oxides / Q000737:chemistry*; D010316:Particle Size; D057057:Serine Proteases / Q000138:chemical synthesis*; D013696:Temperature
chemical_list: D010087:Oxides; D006108:Graphite; D057057:Serine Proteases