Sulfite formation by wine yeasts |
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Authors: | Wolfgang Dott Hans G Trüper |
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Institution: | (1) Institut für Mikrobiologie der Universität, Meckenheimer Allee 168, D-5300 Bonn, Germany |
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Abstract: | The enzyme catalyzing the reduction of sulfite by reduced benzyl viologen (BVH) was partially purified and characterized from two strains of wine yeasts, a sulfite-producing strain and a non-producing strain.Both enzymes showed corresponding features in pH-optima, optima of buffer and benzyl viologen concentrations.The enzymes did not catalyze the reduction of nitrite by reduced viologen dyes, but the reduction of sulfite was uncompetitively inhibited by nitrite. Compounds of sulfur metabolism such as sulfate, thiosulfate, cysteine, serine and methionine did not influence the activity of either of the enzymes. The main differences between the two enzymes exist in the specific activities in crude extracts, the K
m
-values for sulfite, substrate inhibition rates, and localization in different fractions during (NH4)2SO4 precipitation. The specific activity in crude extracts of the sulfite-producing strain (0.052 moles S2- x min-1 x mg-1) was about three fold higher than that of the non-producing strain (0.0179 moles S2- x min-1 x mg-1). On the other hand the sulfite-producing strain had a higher K
m
-value for sulfite (2×10-3 M) and was more strongly inhibited by the substrate than the non-producing strain (6×10-3 M). |
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Keywords: | Wine yeasts Sulfur metabolism Regulation Sulfite reductase |
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