Stereoselective detoxification of chiral sarin and soman analogues by phosphotriesterase.
The catalytic activity of the bacterial phosphotriesterase (PTE) toward a series of chiral analogues of the chemical warfare agents sarin and soman was measured. Chemical procedures were developed for the chiral syntheses of the S(P)- and R(P)-enantiomers of O-isopropyl p-nitrophenyl methylphosphonate (sarin analogue) in high enantiomeric excess. The R(P)-enantiomer of the sarin analogue (k(cat)=2600 s(-1)) was the preferred substrate for the wild-type PTE relative to the corresponding S(P)-enantiomer (k(cat)=290 s(-1)). The observed stereoselectivity was reversed using the PTE mutant, I106A/F132A/H254Y where the k(cat) values for the R(P)- and S(P)-enantiomers were 410 and 4200 s(-1), respectively. A chemo-enzymatic procedure was developed for the chiral synthesis of the four stereoisomers of O-pinacolyl p-nitrophenyl methylphosphonate (soman analogue) with high diastereomeric excess. The R(P)R(C)-stereoisomer of the soman analogue was the preferred substrate for PTE. The k(cat) values for the soman analogues were measured as follows: R(P)R(C,) 48 s(-1); R(P)S(C), 4.8 s(-1); S(P)R(C), 0.3 s(-1), and S(P)S(C), 0.04 s(-1). With the I106A/F132A/H254Y mutant of PTE the stereoselectivity toward the chiral phosphorus center was reversed. With the triple mutant the k(cat) values for the soman analogues were found to be as follows: R(P)R(C,) 0.3 s(-1); R(P)S(C), 0.3 s(-1); S(P)R(C), 11s(-1), and S(P)S(C), 2.1 s(-1). Prior investigations have demonstrated that the S(P)-enantiomers of sarin and soman are significantly more toxic than the R(P)-enantiomers. This investigation has demonstrated that mutants of the wild-type PTE can be readily constructed with enhanced catalytic activities toward the most toxic stereoisomers of sarin and soman.
Li
W S
WS
Department of Chemistry, Texas A&M University, College Station, TX 77842-3012, USA.
Lum
K T
KT
Chen-Goodspeed
M
M
Sogorb
M A
MA
Raushel
F M
FM
D043303:Aryldialkylphosphatase; D002619:Chemical Warfare Agents / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism*; D004950:Esterases / Q000235:genetics / Q000378:metabolism*; D006868:Hydrolysis; D008658:Inactivation, Metabolic; D007700:Kinetics; D008968:Molecular Conformation; D016297:Mutagenesis, Site-Directed; D012524:Sarin / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism*; D012999:Soman / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism*
D002619:Chemical Warfare Agents; D012999:Soman; D012524:Sarin; D004950:Esterases; D043303:Aryldialkylphosphatase