Activity of Periplasmic Hydrogenase of the intestinal SULFATE-REDUCING BACTERIA

I. V. Kushkevych1, H. L. Antonyak2

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1Institute of Animal Biology of NAAS, V. Stus St., 38, Lviv, 79034, Ukraine

2Ivan Franko National University of Lviv, Hrushevsky St., 4, 79005, Lviv, Ukraine

In this paper we present aperiplasmic hydrogenase activity of the sulfate-reducing bacteria Desulfovibrio pigerVib-7 and Desulfomicrobium sp. Rod-9isolated fromthe human large intestine. Theeffect of temperature and pH as well as substrateconcentration on the hydrogenase activity in the cell-free extracts of the D. pigerVib-7 and Desulfomicrobium sp. Rod-9was studied. The optimal temperature for hydrogenase reaction is +35ºC and pH 8.0 for extracts of both bacterialstrains. Based on experimental data, the analysis of the kinetic properties of the periplasmic hydrogenase by the studied bacteria was carried out. Our experimental data have shown that the kinetic curves of the periplasmic hydrogenase reaction have tendency to saturation. The kinetics of the activity in cell-free extracts of the studied bacteria was consistent to the zero-order reaction in the range of 0–20 min. A monotonic increase in the activity of the enzyme was observed under the influenceof hydrogen in concentrations range from 100 until 2000 µM. The periplasmic hydrogenaseactivity, initial (instantaneous) reaction rate (205.67±18.91 μmol H2/min×mg-1 protein) and maximum rate of thehydrogenase reaction (2500±219 μmol H2/min×mg-1 protein) were significantly higherin the cell-freeextractsoftheD. pigerVib-7 strainthanDesulfomicrobium sp. Rod-9. Michaelis constants (Km) of the activity were similar to each other: 864±73 and 669±62μM for D.pigerVib-7andDesulfomicrobiumsp. Rod-9, respectively. Although values of Km of both enzymes were similar and were not statistically different, they cross the vertical axis at different points.

Keywords: sulfate-reducing bacteria, Hydrogenase activity, toxicity, intestinal microbiocenosis, bowel diseases

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