Abstract
Dissimilatory sulfite reductase activity in different fractions of the sulfate-reducing bacteria Desulfovibrio piger Vib-7 and Desulfomicrobium sp. Rod-9 isolated from human intestine was studied. Sulfite reductase, an important enzyme in the process of sulfur metabolism in these bacteria, was solubilized from the membrane fraction. The highest activity of the enzyme in the cell-free extract of the bacterial strains was measured (0.032±0.0026 and 0.028±0.0022 U×mg -1 protein for D. piger Vib-7 and Desulfomicrobium sp. Rod-9, respectively) compared to other fractions. The optimal temperature (+30…35 °C) and pH 7.0 for sulfite reductase reaction in the extracts of both bacterial strains was determined. The spectral analysis of purified sulfite reductase from cell-free extracts was carried out. The absorption maxima were 284, 391, 412, 583, and 630 nm, as well as 287, 393, 545, and 581 nm for sulfite reductase of D. piger Vib-7 and Desulfomicrobium sp. Rod-9, respectively. Analysis of the kinetic properties of the bacterial sulfite reductase has been carried out. The sulfite reductase activity, initial (instantaneous) reaction rate ( V 0 ) and maximum rate of the sulfite reductase reaction ( V max ) were higher in the D. piger Vib-7 cells than in the Desulfomicrobium sp. Rod-9. However, Michaelis constants ( K m ) of the enzyme activity were similar for both bacterial strains. The studies of the sulfite reductase activity, the kinetic properties of this enzyme in the intestinal sulfate-reducing bacteria strains, and their production of hydrogen sulfide in detail can be useful for clarification of the etiological role of these bacteria in the development of inflammatory bowel diseases in humans and animals. Keywords : sulfate-reducing bacteria, sulfite reductase, intestinal microbiocenosis, inflammatory bowel diseases, ulcerative colitis.
Highlights
Sulfate-reducing bacteria occur in the gut flora of about 50 % of healthy persons where they metabolize hydrogen and low molecular weight organic compounds [4]
The studies of the sulfite reductase activity, the kinetic properties of this enzyme in the intestinal sulfate-reducing bacteria strains, and their production of hydrogen sulfide in detail can be useful for clarification of the etiological role of these bacteria in the development of inflammatory bowel diseases in humans and animals
Results of this study showed that the highest specific activity of the enzyme was measured in cell-free extracts
Summary
Sulfate-reducing bacteria occur in the gut flora of about 50 % of healthy persons where they metabolize hydrogen and low molecular weight organic compounds [4]. Fafula hydrogen sulfide and acetate which can be cytotoxic to intestinal cells causing various inflammatory bowel diseases. Hydrogen sulfide accumulated in the human intestine is carcinogenic to its cells and can cause inhibition of cytochrome oxidase, oxidation processes butyrate by colonocytes, and destruction of epithelial cells, develop ulcers, inflammation with subsequent development of colon cancer [2, 10]. The production of highly toxic sulfide from Desulfovibrio desulfuricans has been implicated in the onset of a chronic inflammatory large bowel disease, ulcerative colitis, patients with this disease showing elevated levels of sulfide production and a universal carriage rate of the sulfatereducing bacteria [3, 4]
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