Purification and properties of soman-hydrolyzing enzyme from human liver

A protein nanocomposite for ultra-fast, efficient and non-irritating skin decontamination of nerve agents

In recent assassinations reported in London and Malaysia, nerve agents were used to cause death, by skin poisoning. Skin decontamination is the ultimate and most important defense against nerve agent poisoning, because no effective antidote currently exists. However, almost no existing material can achieve effective and rapid decontamination without irritating the skin. This study links proteins that exhibit no decontamination ability with polymers to form a nanocomposite. This creates a nanospace on the surface of the protein that attracts and traps organic molecules, effectively adsorbing the nerve agent Soman within several seconds, without irritating the skin. Analysis of the different components of proteins and polymers reveals that the decontamination efficiency is considerably affected by the thickness of the coated polymer. Moreover, the thickness of the layer is predominantly determined by the size and species of the core and the crosslinking method. Further in vivo experiments on rats poisoned with Soman verify the efficiency and safety of the nanocomposite. These results could be used to design and synthesize more multi-functional and effective decontamination materials.

Prolidase function in proline metabolism and its medical and biotechnological applications

Prolidase is a multifunctional enzyme that possesses the unique ability to degrade imidodipeptides in which a proline or hydroxyproline residue is located at the C-terminal end. Prolidases have been isolated from archaea and bacteria, where they are thought to participate in proline recycling. In mammalian species, prolidases are found in the cytoplasm and function primarily to liberate proline in the final stage of protein catabolism, particularly during the biosynthesis and degradation of collagen. Collagen comprises nearly one-third of the total protein in the body, and it is essential in maintaining tissue structure and integrity. Prolidase deficiency (PD), a rare autosomal recessive disorder in which mutations in the PEPD gene affect prolidase functionality, tends to have serious and sometimes life-threatening clinical symptoms. Recombinant prolidases have many applications and have been investigated not only as a possible treatment for PD, but also as a part of anti-cancer strategies, a component of biodecontamination cocktails and in the dairy industry. This review will serve to discuss the many in vivo functions of procaryotic and eucaryotic prolidases, as well as the most recent advances in therapeutic and biotechnological application of prolidases.

Butyrylcholinesterase for protection from organophosphorus poisons: catalytic complexities and hysteretic behavior

Butyrylcholinesterase is a promiscuous enzyme that displays complex kinetic behavior. It is toxicologically important because it detoxifies organophosphorus poisons (OP) by making a covalent bond with the OP. The OP and the butyrylcholinesterase are both inactivated in the process. Inactivation of butyrylcholinesterase has no adverse effects. However, inactivation of acetylcholinesterase in nerve synapses can be lethal. OP-inhibited butyrylcholinesterase and acetylcholinesterase can be reactivated with oximes provided the OP has not aged. Strategies for preventing the toxicity of OP include (a) treatment with an OP scavenger, (b) reaction of non-aged enzyme with oximes, (c) reactivation of aged enzyme, (d) slowing down aging with peripheral site ligands, and (e) design of mutants that rapidly hydrolyze OP. Option (a) has progressed through phase I clinical trials with human butyrylcholinesterase. Option (b) is in routine clinical use. The others are at the basic research level. Butyrylcholinesterase displays complex kinetic behavior including activation by positively charged esters, ability to hydrolyze amides, and a lag time (hysteresis) preceding hydrolysis of benzoylcholine and N-methylindoxyl acetate. Mass spectrometry has identified new OP binding motifs on tyrosine and lysine in proteins that have no active site serine. It is proposed, but not yet proven, that low dose exposure involves OP modification of proteins that have no active site serine.

Development and application of acute exposure guideline levels (AEGLs) for chemical warfare nerve and sulfur mustard agents

Acute exposure guideline levels (AEGLs) have been developed for the chemical warfare agents GB, GA, GD, GF, VX, and sulfur mustard. These AEGLs were approved by the National Advisory Committee for Acute Exposure Guideline Levels for Hazardous Substances after Federal Register publication and comment, and judged as scientifically valid by the National Research Council Committee on Toxicology Subcommittee on AEGLs. AEGLs represent general public exposure limits for durations ranging from 10 min to 8 h, and for three levels of severity (AEGL-1, AEGL-2, AEGL-3). Mild effects are possible at concentrations greater than AEGL-1, while life-threatening effects are expected at concentrations greater than AEGL-3. AEGLs can be applied to various civilian and national defense purposes, including evacuation and shelter-in-place protocols, reentry levels, protective clothing specifications, and analytical monitoring requirements. This report documents development and derivation of AEGL values for six key chemical warfare agents, and makes recommendations for their application to various potential exposure scenarios.

Dual activities of human prolidase

The cDNA encoding human liver prolidase derived from a healthy adult's liver was cloned into the expression vector pPIC9K of Pichia pastoris to construct the recombination expression vector pPIC9K-P. The pPIC9K-P was digested by restriction enzyme Pme I, and then transformed into P. pastoris GS115 by electroporation. Transformants (the insertion recombinant) were induced by methanol to express the recombination protein. The optimal induction conditions (medium pH, methanol concentration and induction time) of the insertion transformant with the highest enzymatic activity were estimated by orthogonal experimental design L9(3(4)). The SDS-PAGE of the recombinant human prolidase (rh-prolidase) in induction medium showed a molecular weight of 73 kDa. The activities of the rh-prolidase and organophosphoric acid anhydrolases (OPAA) were assayed by colorimetric methods. The recombinant enzyme catalyzed the hydrolysis of organophosphorous compound soman as well as the hydrolysis of dipeptide Gly-Pro. Under the optimal induction conditions, the maximal activities of prolidase and OPAA came to 44.1 and 54.8 nmol/min/mg protein respectively in the medium supernatant. The rh-prolidase purified from the supernatant by ion exchange gradient chromatography (DEAE-Sepharose Fast Flow) and gel filtration chromatography (Sephacryl S-200 High Resolution) showed a single band by SDS-PAGE analysis. The purified rh-prolidase could decompose soman via hydrolytic reaction in vitro.

Purification and characterization of recombinant human liver prolidase expressed in Saccharomyces cerevisiae

The recombinant human liver prolidase (rh-prolidase, EC 3.4.13.9) from the lysate supernatant of engineering yeast Saccharomyces cerevisiae was purified in two steps employing anion-exchange gradient chromatography (DEAE-Sepharose fast flow) and gel filtration chromatography (Sephacryl S-200 high resolution). The purified recombinant protein furnished a single band with a molecular weight of 56 kD. Intensity scanning of the SDS-PAGE gel revealed that the prolidase accounted for more than 90% of total protein. The optimum pH of the catalytic reaction was 8.0. The enzyme was stimulated by Mn2+, but strongly inhibited by Cu2+ and Zn2+. The rh-prolidase expressed in S. cerevisiae had both dipeptidase and organophosphorus acid anhydrolase activity. It catalyzed the hydrolysis of soman and the dipeptide Gly -Pro. In a detoxification test in vitro, purified rh-prolidase was remarkably efficient at eliminating the toxicity of a lethal dose of soman, with the result that mice survived injection of such a dose.

Toxicokinetics of the nerve agent (+/-)-VX in anesthetized and atropinized hairless guinea pigs and marmosets after intravenous and percutaneous administration

In continuation of our investigations on the toxicokinetics of the volatile nerve agents C(+/-)P(+/-)-soman and (+/-)-sarin, we now report on the toxicokinetics of the rather nonvolatile agent (+/-)-VX. A validated method was developed to determine blood levels of (+/-)-VX by means of achiral gas chromatography at blood levels > or =10 pg/ml. The ratio of the two enantiomers of VX in blood could be measured at levels > or =1 ng/ml by using chiral HPLC in combination with off-line gas chromatographic analysis. In order to obtain basic information on the toxicokinetics of (+/-)-VX, i.e., under conditions of 100% bioavailability, the blood levels of this agent were measured in hairless guinea pigs at iv doses corresponding with 1 and 2 LD50. The derived AUCs indicate a reasonable linearity of the toxicokinetics with dose. Also, the toxicokinetics in marmoset primates was studied at an absolute iv dose corresponding with 1 LD50 in the hairless guinea pig which led to approximately the same levels of (+/-)-VX in blood as observed at 2 LD50 in the hairless guinea pig. Finally, the toxicokinetics of (+/-)-VX were measured in hairless guinea pigs via the most relevant porte d' entrée for this agent, which is the percutaneous route at a dose corresponding with 1 LD50 (pc). Large variations were observed between individual animals in the rate of penetration of (+/-)-VX and in concomitant progression of AChE inhibition in blood of these animals. Blood levels of (+/-)-VX increased gradually over a 6-h period of time. After a 7-h penetration period, the total AUC corresponded with 2.5% bioavailability relative to iv administration. In contrast with the G-agents C(+/-)P(+/-)-soman and (+/-)-sarin, stereospecificity in the sequestration of the two enantiomers of (+/-)-VX is not a prominent phenomenon. It appears that (+/-)-VX is substantially more persistent in vivo than the two G-agents. This persistence may undermine the efficacy of pretreatment with carbamates of percutaneous intoxication in particular due to gradual replacement of carbamate on AChE by (+/-)-VX, whereas classical treatment of intoxication with oximes is hampered by the short persistence of oximes relative to the agent.