Spectrophotometric assay for protease activity in ionic liquids using chromogenic substrates.
A new spectrophotometric assay has been developed to evaluate protease activity in ionic liquids (ILs). The assay consists of two strategies to enable real-time spectrometric analysis of enzymatic reaction in ILs. First, enzymes are modified with a comb-shaped poly(ethylene glycol), PM(13), to obtain a transparent enzyme solution in IL. Second, a chromogenic substrate is used to follow the enzymatic reaction in IL. p-Nitroaniline-derivatized substrates are subjected to protease-catalyzed alcoholysis to release chromogenic p-nitroaniline that can be quantitatively detected by a UV-Vis spectrophotometer. By using this method, we can evaluate protease activity in ILs quite easily without separation of products from the reaction mixture. The availability of the novel assay system was demonstrated in a kinetic analysis of subtilisin-catalyzed reaction in the IL 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([Emim][Tf(2)N]) under different reaction conditions. Because two different serine proteases, subtilisin and alpha-chymotrypsin, substantially retained its original substrate specificity in the IL, the assay can be extended to other enzymes by using suitable chromogenic substrates.
Nakashima
Kazunori
K
Department of Applied Chemistry, Graduate School of Engineering, and Center for Future Chemistry, Kyushu University, Fukuoka 819-0395, Japan.
Maruyama
Tatsuo
T
Kamiya
Noriho
N
Goto
Masahiro
M
D000042:Absorption; D000814:Aniline Compounds / Q000737:chemistry; D002863:Chromogenic Compounds / Q000378:metabolism*; D052578:Ionic Liquids / Q000737:chemistry*; D007700:Kinetics; D008299:Maleic Anhydrides / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry; D015203:Reproducibility of Results; D012697:Serine Endopeptidases / Q000737:chemistry / Q000378:metabolism*; D012995:Solubility; D013056:Spectrophotometry, Ultraviolet; D013379:Substrate Specificity
D000814:Aniline Compounds; D002863:Chromogenic Compounds; D052578:Ionic Liquids; D008299:Maleic Anhydrides; C054144:polyoxyethylene allylmethyl diether-maleic anhydride copolymer; C019498:4-nitroaniline; D011092:Polyethylene Glycols; D012697:Serine Endopeptidases