Potential inhibitor of adenylyl sulfate reductase isolated from Desulfovibrio desulfuricans with PU/PU-Ag to control pitting corrosion of oil tanks and pipelines.

Background and Aim: This study aims to alleviate the microbiologically affected corrosion that occurred by sulfate-reducing bacteria (SRB) through synthesizing a bio-based polyurethane polymer and its nanocomposite coating, silver nanoparticles (PU-Ag). Moreover, this study aims to evaluate the effect of PU alone and PU-Ag as inhibitors for adenylyl sulfate reductase (APS), which is the main enzyme for sulfate reduction. Methods: In this study, the PU was prepared from the vegetable soybean oil, and the silver nanoparticles (Ag-NPs) with a concentration of 1% were coated to the PU, forming a nanocomposite. The PU and the PU-Ag were characterized and evaluated as inhibitors of the APS reductase enzyme. Results: The results obtained from FTIR, UV, DLS, TEM, and XRD confirmed the preparation structure of the PU and PU-Ag. Furthermore, the PU/PU-Ag competitively inhibited the APS reductase with an inhibition constant equal to 35.7 and 11 mg, respectively. These indicated the exert inhibitory effect of PU/PU-Ag upon the activity of the APS reductase enzyme. Conclusion: The APS reductase enzyme produced by SRB, which is recorded as a big problem in the oil and gas industry, such as pitting corrosion of tanks and pipelines, could be inhibited by PU and PU-Ag.

3D-QSAR study of adenosine 5’-phosphosulfate (APS) analouges as ligands for APS reductase

Metabolism of sulfur (sulfur assimilation pathway, SAP) is one of the key pathways for the pathogenesis and survival of persistant bacterias, such as Mycobacterium tuberculosis (Mtb), in the latent period. Adenosine 5?-phospho-sulfate reductase (APSR) is an important enzyme involved in the SAP, absent from the human body, so it might represents a valid target for development of new antituberculosis drugs. This work aimed to develop 3D QSAR model based on the crystal structure of APSR from Pseudomonas aeruginosa, which shows high degree of homology with APSR from Mtb, in complex with its substrate, adenosine 5?-phosphosulfate (APS). 3D QSAR model was built from a set of 16 nucleotide analogues of APS using alignment-independent descriptors derived from molecular interaction fields (MIF). The model improves the understanding of the key characteristics of molecules necessary for the interaction with target, and enables the rational design of novel small molecule inhibitors of Mtb APSR.

Adenosine-5′-Phosphosulfate- and Sulfite Reductases Activities of Sulfate-Reducing Bacteria from Various Environments

A comparative study of the kinetic characteristics (specific activity, initial and maximum rate, and affinity for substrates) of key enzymes of assimilatory sulfate reduction (APS reductase and dissimilatory sulfite reductase) in cell-free extracts of sulphate-reducing bacteria (SRB) from various biotopes was performed. The material for the study represented different strains of SRB from various ecotopes. Microbiological (isolation and cultivation), biochemical (free cell extract preparation) and chemical (enzyme activity determination) methods served in defining kinetic characteristics of SRB enzymes. The determined affinity data for substrates (i.e., sulfite) were 10 times higher for SRB strains isolated from environmental (soil) ecotopes than for strains from the human intestine. The maximum rate of APS reductase reached 0.282–0.862 µmol/min×mg−1 of protein that is only 10 to 28% higher than similar initial values. The maximum rate of sulfite reductase for corrosive relevant collection strains and SRB strains isolated from heating systems were increased by 3 to 10 times. A completely different picture was found for the intestinal SRB Vmax in the strains Desulfovibrio piger Vib-7 (0.67 µmol/min × mg−1 protein) and Desulfomicrobium orale Rod-9 (0.45 µmol/min × mg−1 protein). The determinant in the cluster distribution of SRB strains is the activity of the terminal enzyme of dissimilatory sulfate reduction—sulfite reductase, but not APS reductase. The data obtained from the activity of sulfate reduction enzymes indicated the adaptive plasticity of SRB strains that is manifested in the change in enzymatic activity.

C-terminal Redox Domain of Arabidopsis APR1 is a Non-Canonical Thioredoxin Domain with Glutaredoxin Function

Sulfur is an essential nutrient that can be converted into utilizable metabolic forms to produce sulfur-containing metabolites in plant. Adenosine 5′-phosphosulfate (APS) reductase (APR) plays a vital role in catalyzing the reduction of activated sulfate to sulfite, which requires glutathione. Previous studies have shown that the C-terminal domain of APR acts as a glutathione-dependent reductase. The crystal structure of the C-terminal redox domain of Arabidopsis APR1 (AtAPR1) shows a conserved α/β thioredoxin fold, but not a glutaredoxin fold. Further biochemical studies of the redox domain from AtAPR1 provided evidence to support the structural observation. Collectively, our results provide structural and biochemical information to explain how the thioredoxin fold exerts the glutaredoxin function in APR.

Structural biology of plant sulfur metabolism: from sulfate to glutathione

Sulfur is an essential element for all organisms. Plants must assimilate this nutrient from the environment and convert it into metabolically useful forms for the biosynthesis of a wide range of compounds, including cysteine and glutathione. This review summarizes structural biology studies on the enzymes involved in plant sulfur assimilation [ATP sulfurylase, adenosine-5'-phosphate (APS) reductase, and sulfite reductase], cysteine biosynthesis (serine acetyltransferase and O-acetylserine sulfhydrylase), and glutathione biosynthesis (glutamate-cysteine ligase and glutathione synthetase) pathways. Overall, X-ray crystal structures of enzymes in these core pathways provide molecular-level information on the chemical events that allow plants to incorporate sulfur into essential metabolites and revealed new biochemical regulatory mechanisms, such as structural rearrangements, protein–protein interactions, and thiol-based redox switches, for controlling different steps in these pathways.

Crystallization of the C-terminal redox domain of the sulfur-assimilatory enzyme APR1 fromArabidopsis thaliana

Plant-type APS reductase (APR), which catalyzes the reduction of activated sulfate to sulfite in plants, consists of a reductase domain and a C-terminal redox domain showing sequence homology to thioredoxin but possessing the activity of glutaredoxin. In order to understand the structural and biochemical properties of the redox domain of plant-type APS reductase, the C-terminal domain of APR1 (APR1C) fromArabidopsis thalianawas crystallized using the sitting-drop vapour-diffusion method. X-ray diffraction data were collected to a resolution of 2.70 Å on the SPXF beamline BL13B1 at the NSRRC, Taiwan. The crystals belonged to space groupP43212 orP41212, with unit-cell parametersa=b= 58.2,c= 86.7 Å. With one molecule per asymmetric unit, the crystal volume per unit protein weight (VM) is 2.64 Å3 Da−1, which corresponds to a solvent content of approximately 53.49%. Further structure-based functional studies of APR1C would extend knowledge of the molecular mechanism and regulation of APR.