Arsenate reductase of Rufibacter tibetensis is a metallophosphoesterase evolved to catalyze redox reactions.

An arsenate reductase (Car1) from the Bacteroidetes species Rufibacter tibetensis 1351T was isolated from the Tibetan Plateau. The strain exhibits resistance to arsenite [As(III)] and arsenate [As(V)] and reduces As(V) to As(III). Here we shed light on the mechanism of enzymatic reduction by Car1. AlphaFold2 structure prediction, active site energy minimization, and steady-state kinetics of wild-type and mutant enzymes give insight into the catalytic mechanism. Car1 is structurally related to calcineurin-like metallophosphoesterases (MPPs). It functions as a binuclear metal hydrolase with limited phosphatase activity, particularly relying on the divalent metal Ni2+. As an As(V) reductase, it displays metal promiscuity and is coupled to the thioredoxin redox cycle, requiring the participation of two cysteine residues, Cys74 and Cys76. These findings suggest that Car1 evolved from a common ancestor of extant phosphatases by incorporating a redox function into an existing MPP catalytic site. Its proposed mechanism of arsenate reduction involves Cys74 initiating a nucleophilic attack on arsenate, leading to the formation of a covalent intermediate. Next, a nucleophilic attack of Cys76 leads to the release of As(III) and the formation of a surface-exposed Cys74-Cys76 disulfide, ready for reduction by thioredoxin.

Widespread Distribution of the arsO Gene Confers Bacterial Resistance to Environmental Antimony.

Microbial oxidation of environmental antimonite (Sb(III)) to antimonate (Sb(V)) is an antimony (Sb) detoxification mechanism. Ensifer adhaerens ST2, a bacterial isolate from a Sb-contaminated paddy soil, oxidizes Sb(III) to Sb(V) under oxic conditions by an unknown mechanism. Genomic analysis of ST2 reveals a gene of unknown function in an arsenic resistance (ars) operon that we term arsO. The transcription level of arsO was significantly upregulated by the addition of Sb(III). ArsO is predicted to be a flavoprotein monooxygenase but shows low sequence similarity to other flavoprotein monooxygenases. Expression of arsO in the arsenic-hypersensitive Escherichia coli strain AW3110Δars conferred increased resistance to Sb(III) but not arsenite (As(III)) or methylarsenite (MAs(III)). Purified ArsO catalyzes Sb(III) oxidation to Sb(V) with NADPH or NADH as the electron donor but does not oxidize As(III) or MAs(III). The purified enzyme contains flavin adenine dinucleotide (FAD) at a ratio of 0.62 mol of FAD/mol protein, and enzymatic activity was increased by addition of FAD. Bioinformatic analyses show that arsO genes are widely distributed in metagenomes from different environments and are particularly abundant in environments affected by human activities. This study demonstrates that ArsO is an environmental Sb(III) oxidase that plays a significant role in the detoxification of Sb(III).

Hypertrophic pachymeningitis with co-occurrence of anti-neutrophil cytoplasmic antibodies and immunoglobulin G4 seropositivity: Case report and literature review.

We report an extremely rare case of hypertrophic pachymeningitis in which a 71-year-old man presented with an intractable recurrent headache for >1 year. During this period, he became positive for immunoglobulin G4 and proteinase 3-antineutrophil cytoplasmic antibodies. Contrast-enhanced magnetic resonance imaging showed characteristic diffuse thickening of the dura. Symptoms were improved by intravenous methylprednisolone (500 mg per day for 5 days) and cyclophosphamide pulse therapy during corticosteroid withdrawal; he remained symptom-free during 1-year follow-up. This case suggests that this disease can be treated by corticosteroids combined with immunosuppressive agents.

Improving the biotransformation of phytosterols to 9α-hydroxy-4-androstene-3,17-dione by deleting embC associated with the assembly of cell envelope in Mycobacterium neoaurum.

The conversion of low value-added phytosterols into 9α-hydroxy-4-androstene-3,17-dione (9-OHAD) by mycobacteria is an important step in the steroid pharmaceutical industry. However, the highly dense cell envelope with extremely low permeability largely affects the overall transformation efficiency. Here, we preliminarily located the key gene embC required for the synthesis of lipoarabinomannan from lipomannan in Mycobacterium neoaurum. The genetic manipulation of embC indicated that it might be the only functional enzyme catalyzing the above synthesis process. The deficiency of lipoarabinomannan led to a significantly increased cell permeability, which in turn caused the enhanced uptake capacity of cells. The sterol substrate conversion efficiency of mycobacterial cells was increased by about 52.4 % after 72-h conversion. Ultimately, the absence of embC increased the productivity from 0.0927 g/L/h to 0.1031 g/L/h, as confirmed by a resting cell system. This study verified the feasibility of improving the efficiency of the microbial conversion system through the cell envelope engineering strategy.

[Treatment of severe active systemic lupus erythematosus by PMC therapy combined langchuang fuzheng jiedu capsule: a clinical observation].

OBJECTIVE: To evaluate the efficacy and safety of PMC therapy (Prednisone, Methotrexate, Chloroquine) combined Langchuang Fuzheng Jiedu Capsule (LFJC), thus choosing a better therapy of integrative medicine for SLE in the period of glucocorticoid use. METHODS: Sixty active SLE patients were randomly assigned to two groups, the control group and the treatment group. Those in the control group received PMC therapy (As for Prednisone, it was given at the daily dose of 1 mg/kg till 2 weeks after the condition being stable or after 8 weeks of treatment. Then the dose was reduced by 10% every two weeks. When the dose was reduced to 0.5 mg/kg daily, it was reduced by 2.5 mg per two weeks. When the dose was reduced to 15 mg daily, the dose was reduced to 2.5 mg per four weeks. As for Methotrexate, 10 mg each time, once a week. As for Chloroquine, 100 mg each time, twice daily), while those in the treatment group received PMC therapy (the same way as that for the control group) combined with LFJC (consisting of Astragalus membranaceus 50 g, Angelica sinensis 20 g, Ligusticum Chuanxiong 20 g, prepared Rehmannia Rhizome 30 g, Herba Serissae 30 g, Centella 30 g, centipede 4 g, scorpions 10 g, nidus versace 12 g, et al., 0.5 g per pill, containing 5.7 g crude drug. When the hormone was given at a large dose, LFJC was administered at 12 pills each time, three times daily). When the hormone was given at a middle dose, LFJC was administered at 8 pills each time, three times daily. When the hormone was given at a small dose, LFJC was administered at 6 pills each time, three times daily. The treatment course was six months. The improvement of symptoms and signs between before and after treatment, SLE disease activity index (SLEDAI), efficacy of Chinese medical syndrome, UPro quantitation, erythrocyte sedimentation rate (ESR), complement 3 (C3), C-reactive protein (CRP), the reduction and withdrawal of hormones, and infection of the respiratory tract were observed. RESULTS: The difference in post-SLEDAI was obviously larger in the treatment group than in the control group (P < 0.05). The fatigue severity scale (FSS) was less after treatment than before treatment in the treatment group, showing statistical difference when compared with that of the control group (P < 0.05). The total effective rate was 93.33% in the treatment group, showing statistical difference when compared with that of the control group (86.66%; chi2 = 6.736, P < 0.05). The ESR decreased after treatment in the treatment group, showing statistical difference when compared with that of the control group (P < 0.01). C3 increased after treatment in the treatment group, showing statistical difference when compared with that of the control group (P < 0.05). The hormone was reduced to (13.70 +/- 5.42) mg/d by the end of the therapeutic course in the treatment group, obviously less than that of the control group [(17.63 +/- 7.80) mg/d, P < 0.05). Seven patients suffered from secondary infection of the respiratory tract infection in the treatment group (5 from upper respiratory tract infection and 2 from lower respiratory tract infection), obviously less than those of the control group (25 from upper respiratory tract infection and 10 from lower respiratory tract infection) (P < 0.05). CONCLUSIONS: PMC combined LFJC was a better treatment program for severe active SLE (SLEDAI > or = 15). It was more safe and effective when compared with using Western medicine alone. It could enhance the efficacy of hormones and help reduction/withdrawal of hormones.