Characterisation of Dermanyssus gallinae glutathione S-transferases and their potential as acaricide detoxification proteins

BACKGROUND: Glutathione S-transferases (GSTs) facilitate detoxification of drugs by catalysing the conjugation of the reduced glutathione (GSH) to electrophilic xenobiotic substrates and therefore have a function in multi-drug resistance. As a result, knowledge of GSTs can inform both drug resistance in, and novel interventions for, the control of endo- and ectoparasite species. Acaricide resistance and the need for novel control methods are both pressing needs for Dermanyssus gallinae, a highly economically important haematophagous ectoparasite of poultry. METHODS: A transcriptomic database representing D. gallinae was examined and 11 contig sequences were identified with GST BlastX identities. The transcripts represented by 3 contigs, designated Deg-GST-1, −2 and −3, were fully sequenced and further characterized by phylogenetic analysis. Recombinant versions of Deg-GST-1, −2 and −3 (rDeg-GST) were enzymically active and acaricide-binding properties of the rDeg-GSTs were established by evaluating the ability of selected acaricides to inhibit the enzymatic activity of rDeg-GSTs. RESULTS: 6 of the identified GSTs belonged to the mu class, followed by 3 kappa, 1 omega and 1 delta class molecules. Deg-GST-1 and −3 clearly partitioned with orthologous mu class GSTs and Deg-GST-2 partitioned with delta class GSTs. Phoxim, permethrin and abamectin significantly inhibited rDeg-GST-1 activity by 56, 35 and 17 % respectively. Phoxim also inhibited rDeg-2-GST (14.8 %) and rDeg-GST-3 (20.6 %) activities. CONCLUSIONS: Deg-GSTs may have important roles in the detoxification of pesticides and, with the increased occurrence of acaricide resistance in this species worldwide, Deg-GSTs are attractive targets for novel interventions

Structure and Function of Enzymes Involved in the Biosynthesis of Tropane Alkaloids

Tropane alkaloids are found in a scattered distribution among the angiosperm families including members within the Solanaceae, Erythroxylaceae, Convolvulaceae, and Brassicaceae. Recent studies regarding the origins of tropane production provide strong evidence for a polyphyletic origin, suggesting that novel enzymes from different gene families have been recruited during the course of flowering plant evolution. Tropane alkaloid biosynthesis is best documented on the molecular genetic and biochemical level from solanaceous species. Regardless of the system chosen, there are currently gaps in the knowledge of enzyme structure-function relationships and how they influence tropane alkaloid biosynthesis. Obtaining insights on structure-function relationships of tropane biosynthetic enzymes is critical to understanding regulation, turnover, and flux of metabolites through the pathway. In this review, we discuss the current state of knowledge regarding structure-function relationships of the known steps involved in tropane biosynthesis.This is a post-peer-review, pre-copyedit version of a chapter published as Kim, Neill, Benjamin Chavez, Charles Stewart, and John C. D’Auria. "Structure and Function of Enzymes Involved in the Biosynthesis of Tropane Alkaloids." In Tropane Alkaloids (Srivastava V., Mehrotra S., Mishra S., eds.) 2021: 21-50. The final authenticated version is available online at DOI: 10.1007/978-981-33-4535-5_2. Posted with permission.</p