Molecular Interaction between Organophosphorus Acid Anhydrolase and Diisopropylfluorophosphate

Abstract

Organophosphorus acid anhydrolases (OPAA; E.C.3.1.8.2) are a class of enzymes that hydrolyze a variety of toxic acetylcholinesterase-inhibiting organophosphorus (OP) compounds, including pesticides and fluorine-containing chemical nerve agents. In this paper, subphase conditions have been optimized to obtain stable OPAA Langmuir films, and the diisopropylfluorophosphate (DFP) hydrolysis reaction catalyzed by OPAA in aqueous solution and at the air-water interface was studied. OPAA-DFP interactions were investigated utilizing different spectroscopic techniques, that is, circular dichroism and fluorescence in aqueous solution and infrared reflection absorption spectroscopies at the air-water interface. The characterization of OPAA and its secondary structure in aqueous solution and as a monolayer at the air-water interface in the absence and in the presence of DFP dissolved in aqueous solution or in the aqueous subphase demonstrated significantly distinctive features. The research described herein demonstrated that OPAA can be used in an enzyme-based biosensor for DFP detection.

Surface Properties of “Jellyfish”: Langmuir Monolayer and Langmuir−Blodgett Film Studies of Recombinant Aequorin

“…To quantify the content in percentage of the secondary structures of aequorin aqueous solutions, the CD spectra were analyzed by the program CDPro , and the results are shown in Table . The reason to choose CDPro was that CDPro included the three popular methods for CD spectra analysis: SELCON3, CONTIN, and CDSSTR. ,− The assignment of CD spectra from CDPro gave the content of six secondary structural classes: regular α-helix, α R ; distorted α-helix, α D ; regular β-sheet, β R ; distorted β-sheet, β D ; turns, T; and unordered, U. When the pH increased from 7.6 to 9.0, the content of regular α-helix decreased from 21.2% to 17.2% and the content of distorted α-helix decreased from 16.6% to 15.0%.…”

Organophosphorus acid anhydrolase fromAlteromonas macleodii: structural study and functional relationship to prolidases

“…In contrast to OPH, the natural substrate and role of which are still unknown, OPAA has been identified as a proline dipeptidase (Cheng et al, 1997), which means that it can cleave the P-F bond in G-type nerve agents as well as dipeptides containing a C-terminal proline residue (Xaa-Pro). OPAA from Alteromonas species (aOPAA) hydrolyses DFP at a high rate (V max = 2.70 mV s À1 obtained using a pH electrode; K m = 0.54 mM with DFP as substrate; Zheng et al, 2005). aOPAA is able to cleave the P-F bond in OPs, while its catalytic activity towards P-O, P-S and P-CN bonds is minimal (Zheng et al, 2005).…”

“…OPAA from Alteromonas species (aOPAA) hydrolyses DFP at a high rate (V max = 2.70 mV s À1 obtained using a pH electrode; K m = 0.54 mM with DFP as substrate; Zheng et al, 2005). aOPAA is able to cleave the P-F bond in OPs, while its catalytic activity towards P-O, P-S and P-CN bonds is minimal (Zheng et al, 2005). Activity assays of aOPAAs towards DFP and several types of G-agents have been described previously (Cheng et al, 1997).…”

“…hydrolysis of OPs. OPH cleaves P-O, P-F, P-S and P-CN bonds via an S N 2 mechanism (Zheng et al, 2005).…”

Infrared Reflection−Absorption Spectroscopy and Polarization-Modulated Infrared Reflection−Absorption Spectroscopy Studies of the Organophosphorus Acid Anhydrolase Langmuir Monolayer

“…[9][10][11][12][13][14] Organophosphorus acid anhydrolase (OPAA; E.C.3.1.8.2), with a molecular weight of 58 500 Da, is one of the enzymes which can be used in the fabrication of sensors to detect OP compounds, because OPAA has a high ability to cleave the P-F bond in OP compounds, for example, diisopropylfluorophosphate (DFP), which has a similar structure to sarin (Scheme 1). 15,16 Langmuir monolayer and Langmuir-Blodgett (LB) film techniques are widely used methods to build up ultrathin film devices and sensors. 10,[17][18][19] The surface chemistry properties of OPAA have been examined in detail to optimize the conditions to make OP sensors by the LB film technique.…”