Glutathione from the New Zealand grass grub, Costelytra zealandica Their isolation and characterization and the effect on their activity of endogenous factors

Preparation of metal–organic frameworks with bimetallic linkers and corresponding properties

A series of metal–organic frameworks (MOFs) with bimetallic linkers were synthesized through a facile reflux route.

Computational interaction analysis of organophosphorus pesticides with different metabolic proteins in humans

Pesticides have the potential to leave harmful effects on humans, animals, other living organisms, and the environment. Several human metabolic proteins inhibited after exposure to organophosphorus pesticides absorbed through the skin, inhalation, eyes and oral mucosa, are most important targets for this interaction study. The crystal structure of five different proteins, PDBIDs: 3LII, 3NXU, 4GTU, 2XJ1 and 1YXA in Homo sapiens (H. sapiens), interact with organophosphorus pesticides at the molecular level. The 3-D structures were found to be of good quality and validated through PROCHECK, ERRAT and ProSA servers. The results show that the binding energy is maximum -45.21 relative units of cytochrome P450 protein with phosmet pesticide. In terms of H-bonding, methyl parathion and parathion with acetylcholinesterase protein, parathion, methylparathion and phosmet with protein kinase C show the highest interaction. We conclude that these organophosphorus pesticides are more toxic and inhibit enzymatic activity by interrupting the metabolic pathways in H. sapiens.

Insect glutathione transferases and insecticide resistance

Glutathione transferases (GSTs) are a diverse family of enzymes found ubiquitously in aerobic organisms. They play a central role in the detoxification of both endogenous and xenobiotic compounds and are also involved in intracellular transport, biosynthesis of hormones and protection against oxidative stress. Interest in insect GSTs has primarily focused on their role in insecticide resistance. GSTs can metabolize insecticides by facilitating their reductive dehydrochlorination or by conjugation reactions with reduced glutathione, to produce water-soluble metabolites that are more readily excreted. In addition, they contribute to the removal of toxic oxygen free radical species produced through the action of pesticides. Annotation of the Anopheles gambiae and Drosophila melanogaster genomes has revealed the full extent of this enzyme family in insects. This mini review describes the insect GST enzyme family, focusing specifically on their role in conferring insecticide resistance.

Glutathione S-transferase in the insect Apis mellifera macedonica kinetic characteristics and effect of stress on the expression of GST isoenzymes in the adult worker bee

The glutathione S-transferase present in the adult worker bee Apis mellifera macedonica was purified and analyzed for its physicochemical and kinetic properties. The enzyme is heterodimeric with subunit molecular masses of 29 and 25 kDa, respectively. Two main isoenzymes with distinct kinetic properties are present, with isoelectric points of 7.40 for the alkaline and 4.58 for the acidic forms, respectively. The two enzymes are induced independently by factors such as insecticide treatments and environmental conditions, including low temperatures or starvation.

Genomic organization and putative promoters of highly conserved glutathione S-transferases originating by alternative splicing in Anopheles dirus

The genomic DNA of a GST class I alternative splicing gene has been characterized from Anopheles dirus, a Thai malaria vector. This gene organization is highly conserved in An. dirus and Anopheles gambiae (aggst1alpha), with >80% nucleotide identity in the coding region. Their gene organization contains six exons for four mature GST transcripts, which share exon 1 and exon 2 but vary between four different exon 3 sequences (exon 3A-3D). The deduced amino acid sequence of the GST transcripts from these two genes also shows very high conservation, with 85-93% identity for each orthologous gene. Two putative promoters and possible regulatory elements were predicted by a combination of the TSSW and MatInspector programs. The Ad214 promoter is proposed to be involved in developmental stage regulation. The Ad2112 promoter would appear to respond to intra- or extracellular stimuli. These two Anopheline species appear to have diverged in the distant past based on gene neighbors and phylogenetic data, yet these GST genes are still conserved. Therefore it is highly probable that this GST gene organization has one or more important roles.

Isoenzymes of glutathione S-transferase from the mosquito Anopheles dirus species B: the purification, partial characterization and interaction with various insecticides

Previously we have purified and characterized a major glutathione S-transferase (GST) activity, GST-4a, from the Thai mosquito Anopheles dirus B, a model mosquito for study of anopheline malaria vectors [Prapanthadara, L. Koottathep, S., Promtet, N., Hemingway, J. and Ketterman, A.J. (1996) Insect Biochem. Mol. Biol. 26:3, 277-285]. In this report we have purified an isoenzyme, GST-4c, which has the greatest DDT-dehydrochlorinase activity. Three additional isoenzymes, GST-4b, GST-5 and GST-6, were also partially purified and characterized for comparison. All of the Anopheles GST isoenzymes preferred 1-chloro-2,4-dinitrobenzene (CDNB) as an electrophilic substrate. In kinetic studies with CDNB as an electrophilic substrate, the V(max) of GST-4c was 24.38 micromole/min/mg which was seven-fold less than GST-4a. The two isoenzymes also possessed different K(m)s for CDNB and glutathione. Despite being only partially pure GST-4b had nearly a four-fold greater V(max) for CDNB than GST-4c. In contrast, GST-4c possessed the greatest DDT-dehydrochlorinase specific activity among the purified insect GST isoenzymes and no activity was detected for GST-5. Seven putative GST substrates used in this study were not utilized by An. dirus GSTs, although they were capable of inhibiting CDNB conjugating activity to different extents for the different isoenzymes. Bromosulfophthalein and ethacrynic acid were the most potent inhibitors. The inhibition studies demonstrate different degrees of interaction of the An. dirus isoenzymes with various insecticides. The GSTs were inhibited more readily by organochlorines and pyrethroids than by the phosphorothioates and carbamate. In a comparison between An. dirus and previous data from An. gambiae the two anopheline species possess a similar pattern of GST isoenzymes although the individual enzymes differ significantly at the functional level. The available data suggests there may be a minimum of three GST classes in anopheline insects.

Insecticide resistance in insect vectors of human disease

Insecticide resistance is an increasing problem in many insect vectors of disease. Our knowledge of the basic mechanisms underlying resistance to commonly used insecticides is well established. Molecular techniques have recently allowed us to start and dissect most of these mechanisms at the DNA level. The next major challenge will be to use this molecular understanding of resistance to develop novel strategies with which we can truly manage resistance. State-of-the-art information on resistance in insect vectors of disease is reviewed in this context.

Cloning and localization of a glutathione S-transferase class I gene from Anopheles gambiae

1,1,1-Trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) resistance in both adults and larvae of Anopheles gambiae is mediated by stage-specific glutathione S-transferases (GSTs). On the basis of their biochemical characteristics the larval resistance-associated GSTs are likely to be insect class I GSTs. Aggst1-2, a class I GST gene, which is expressed in larvae, has been cloned from the malaria vector A. gambiae. The gene was inserted into a bacterial expression system, and the detection of 1-chloro-2,4-dinitrobenzene (CDNB) conjugating activity in Eschericia coli expressing the recombinant enzyme confirmed that aggst1-2 encodes a catalytically active GST. The gene encodes a 209 amino acid protein with 46% sequence similarity to a Drosophila melanogaster class I GST (GST-D1), 44% similarity with a Musca domestica class I GST (MdGST-1), but only low levels of homology with class II insect GSTs, including the adult specific AgGST2-1 from A. gambiae. Southern analysis of genomic DNA indicated that A. gambiae has multiple class I GSTs. In situ hybridization of class I genomic and cDNA clones to polytene chromosomes identified a single region of complementarity on chromosome 2R division 18B, suggesting that these class I GSTs in A. gambiae are arranged sequentially in the genome. Three positive overlapping recombinant clones were identified from an A. gambiae genomic library. Mapping and partial sequencing of these clones suggests that there are several GSTs and truncated GST pseudogenes within the 30kb of DNA that these clones span.

Purification and characterization of a major glutathione S-transferase from the mosquito Anopheles dirus (species B)

The major form of glutathione S-transferase (GST) activity from the mosquito Anopheles dirus (species B), a vector of malaria in Thailand has been purified 421-fold. It constituted approx. 20% of the total measured CDNB conjugating activity in the homogenate. This enzyme appeared as a single band of 25.0 +/- 0.26 kDa on SDS-PAGE and was kinetically characterized with 10 substrates and 4 inhibitors. The enzyme is capable of catalysing dehydrochlorination of 1,1,1-trichloro-2,2-bis-(p-chlorophenyl)ethane (DDT) in vitro at a rate of 4.4 nmol of 1,1-dichloro-2,2-bis-(p-chlorophenyl)ethane (DDE) formation per mg protein. This is comparable to the rate of catalysis of the orthologous isoenzyme from An. gambiae reported previously. The IC50 plots of the inhibitor data (fractional velocity vs log [I]) for three of the inhibitors indicate the homogenous nature of this enzyme. However, inhibition by ethacrynic acid demonstrates more than a single affinity site for interaction. The six N-terminal amino acids of the purified enzyme are identical to a GST reported from Aedes aegypti, which was indicated to play a role in DDT-resistance in this species. The results suggest that the two enzymes may belong to the same class, however each possesses a different specificity.

Synthesis and use of an isoform-specific affinity matrix in the purification of glutathione S-transferases from the housefly, Musca domestica (L.)

Glutathione may be linked to an agarose matrix which has been activated by treatment with epichlorhydrin. The resulting resin displayed group selectivity for the glutathione S-transferases of the housefly Musca domestica (L). The isoenzymes of low isoelectric point, which have little activity with substrates other than 1-chloro-2,4-dinitrobenzene, bound strongly to this matrix and were eluted with 10 mM glutathione at pH 7.4. On the other hand, the group of isoenzymes of higher isoelectric point, showing activity with other substrates such as 3,4-dichloronitrobenzene, did not bind. These isoenzymes did bind to a sulfobromophthalein-glutathione conjugate immobilized on agarose and could be eluted with 5 mM sulfobromophthalein at pH 7.4. The immobilized glutathione resin bound rat liver glutathione S-transferase subunits from all three molecular weight classes.

Microplate assay of glutathione s-transferase activity for resistance detection in single-mosquito triturates

1. Optimum conditions are described for a simple, rapid microplate assay that measures glutathione s-transferase (GST) activity accurately and precisely in small portions of single mosquito homogenates. 2. Up to 10 assay replicates were possible for individual adults and larvae. Concentration of GST activity in the head/thorax region allows blood-fed mosquitoes with abdomens removed to be used in assays. 3. The method allows the use of GST activity as a biochemical character in comparative studies of populations. 4. The microplate assay detects elevated GST activities associated with DDT resistance in Anopheles arabiensis.