Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut 06269.
Appl Environ Microbiol. 1994 Jul;60(7):2622-6. doi: 10.1128/aem.60.7.2622-2626.1994.
The growth of the hyperthermophilic, anaerobic bacterium Thermotoga neapolitana is stimulated by elemental sulfur by an unknown mechanism. We detected hydrogen-dependent sulfur reductase (sulfhydrogenase) and polysulfide dehydrogenase activities in cell extracts of this organism, demonstrating that it has at least two pathways for sulfidogenesis. Hydrogen-dependent sulfur reductase and hydrogenase activities are catalyzed by the purified hydrogenase of Thermotoga maritima, and this enzyme was called the sulfhydrogenase (K. Ma, R. N. Schicho, R. M. Kelly, and M. W. W. Adams, Proc. Natl. Acad. Sci. USA 90:5341-5344, 1993). Cells grown without elemental sulfur or cystine had 1.3 to 3.3 times higher sulfhydrogenase activities than those grown with either of these sources of sulfane sulfur. Hydrogenase activity was 2 to 5 times higher. Polysulfide dehydrogenase was up to 48-fold more active in cell extracts than the sulfhydrogenase. The activity of polysulfide dehydrogenase was approximately twofold higher when cells were grown in the presence of elemental sulfur. Its activity was oxygen labile in crude extracts, and it appears to be a cytoplasmic enzyme. Polysulfide was preferred over elemental sulfur as an electron acceptor (K(m) = 0.15 mM) and was more active with NADH (K(m) = 0.03 mM) than NADPH (K(m) = 0.41 mM). Growth in the presence of elemental sulfur appeared to slightly increase the activity of polysulfide dehydrogenase and slightly decrease both activities of sulfhydrogenase (hydrogenase and polysulfide reductase), while growth without elemental sulfur had the opposite effects. The greater activity of polysulfide dehydrogenase and its apparent regulation indicate that it is the more physiologically important means of polysulfide reduction.
产甲烷嗜热厌氧杆菌的生长受元素硫的刺激，但具体机制尚不清楚。我们在该菌的细胞提取物中检测到了依赖于氢的硫还原酶（氢化酶）和多硫化物脱氢酶活性，这表明其至少有两种硫化物生成途径。依赖于氢的硫还原酶和氢化酶活性由纯化的海洋栖热菌氢化酶催化，这种酶被称为氢化酶（K. Ma、R. N. Schicho、R. M. Kelly 和 M. W. W. Adams，Proc. Natl. Acad. Sci. USA 90:5341-5344，1993）。在没有元素硫或半胱氨酸的情况下生长的细胞的氢化酶活性比用这些含硫化合物作为硫源时高 1.3 到 3.3 倍。氢化酶活性高 2 到 5 倍。多硫化物脱氢酶在细胞提取物中的活性比氢化酶高 48 倍。当细胞在元素硫存在下生长时，多硫化物脱氢酶的活性约高 2 倍。粗提取物中，该酶的活性对氧气敏感，似乎是一种细胞质酶。多硫化物作为电子受体比元素硫更有效（K(m) = 0.15 mM），并且 NADH（K(m) = 0.03 mM）比 NADPH（K(m) = 0.41 mM）更有效。在元素硫存在下生长似乎略微增加了多硫化物脱氢酶的活性，略微降低了氢化酶（氢化酶和多硫化物还原酶）的两种活性，而在没有元素硫的情况下生长则产生相反的效果。多硫化物脱氢酶的高活性及其明显的调节表明，它是多硫化物还原的更重要的生理途径。
