Crystal structures of human group-VIIA phospholipase A2 inhibited by organophosphorus nerve agents exhibit non-aged complexes.

نویسندگان

  • Uttamkumar Samanta
  • Stephen D Kirby
  • Prabhavathi Srinivasan
  • Douglas M Cerasoli
  • Brian J Bahnson
چکیده

The enzyme group-VIIA phospholipase A2 (gVIIA-PLA2) is bound to lipoproteins in human blood and hydrolyzes the ester bond at the sn-2 position of phospholipid substrates with a short sn-2 chain. The enzyme belongs to a serine hydrolase superfamily of enzymes, which react with organophosphorus (OP) nerve agents. OPs ultimately exert their toxicity by inhibiting human acetycholinesterase at nerve synapses, but may additionally have detrimental effects through inhibition of other serine hydrolases. We have solved the crystal structures of gVIIA-PLA2 following inhibition with the OPs diisopropylfluorophosphate, sarin, soman and tabun. The sarin and soman complexes displayed a racemic mix of P(R) and P(S) stereoisomers at the P-chiral center. The tabun complex displayed only the P(R) stereoisomer in the crystal. In all cases, the crystal structures contained intact OP adducts that had not aged. Aging refers to a secondary process OP complexes can go through, which dealkylates the nerve agent adduct and results in a form that is highly resistant to either spontaneous or oxime-mediated reactivation. Non-aged OP complexes of the enzyme were corroborated by trypsin digest and matrix-assisted laser desorption ionization mass spectrometry of OP-enzyme complexes. The lack of stereoselectivity of sarin reaction was confirmed by gas chromatography/mass spectrometry using a chiral column to separate and quantitate the unbound stereoisomers of sarin following incubation with enzyme. The structural details and characterization of nascent reactivity of several toxic nerve agents is discussed with a long-term goal of developing gVIIA-PLA2 as a catalytic bioscavenger of OP nerve agents.

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

Crystal Structure of Patatin-17 in Complex with Aged and Non-Aged Organophosphorus Compounds

Patatin is a non-specific plant lipase and the eponymous member of a broad class of serine hydrolases termed the patatin-like phospholipase domain containing proteins (PNPLAs). Certain PNPLA family members can be inhibited by organophosphorus (OP) compounds. Currently, no structural data are available on the modes of interaction between the PNPLAs and OP compounds or their native substrates. To...

متن کامل

P 25: The Facilitatory Action of Snake Venom Phospholipase A2 Neurotoxins by Which Increase the Release of Acetylcholine, May Improve Alzheimer\'s Disease Symptoms

Introduction: In a serious brain disorder like Alzheimer's disease, the levels of acetylcholine (Ach) drop significantly. The gradual death of cholinergic brain cells leads to a profound loss of memory and learning ability. Acetylcholine is the chemical messenger that sends messages from one neuron to another in the area of the brain used for memory. Many of the current medications act to enhan...

متن کامل

Crystal structure of bovine pancreatic phospholipase A2 covalently inhibited by p-bromo-phenacyl-bromide.

Bovine pancreatic phospholipase A2 covalently inhibited by p-bromo-phenacyl-bromide was crystallized from 50% (v/v) 2-methyl-2,4-pentanediol. The space group was P3(1)21 with cell dimensions a = b = 46.73 A and c = 102.5 A (1 A = 0.1 nm). Diffraction data were collected by oscillation photography from one single crystal of dimensions 0.2 mm x 0.2 mm x 0.2 mm. The crystal structure was determine...

متن کامل

Docking Studies, Synthesis, and In-vitro Evaluation of Novel Oximes Based on Nitrones as Reactivators of Inhibited Acetylcholinesterase

Acetylcholinesterase has important role in synaptic cleft. It breaks down the acetylcholineatcholinergic synapsesand terminates the cholinergic effects. Some chemical agents likeorganophosphorus compounds (OPCs) including nerve agents and pesticides react withacetylcholinesteraseirreversibly. They inhibit normal biological enzyme action and resultin accumulation of acetylcholineand show toxic e...

متن کامل

Crystal structure of human butyrylcholinesterase and of its complexes with substrate and products.

Cholinesterases are among the most efficient enzymes known. They are divided into two groups: acetylcholinesterase, involved in the hydrolysis of the neurotransmitter acetylcholine, and butyrylcholinesterase of unknown function. Several crystal structures of the former have shown that the active site is located at the bottom of a deep and narrow gorge, raising the question of how substrate and ...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

عنوان ژورنال:
  • Biochemical pharmacology

دوره 78 4  شماره 

صفحات  -

تاریخ انتشار 2009