Chiong M, González E, Barra R, Vásquez C
Laboratorio de Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santiago.
J Bacteriol. 1988 Jul;170(7):3269-73. doi: 10.1128/jb.170.7.3269-3273.1988.
Cell-free extracts of Thermus thermophilus HB8 catalyze the in vitro, NADH-dependent reduction of potassium tellurite (K2TeO3). Three different protein fractions with tellurite-reducing activities were identified. Two exhibited high molecular weight and were composed of at least two different polypeptides. The protein in the third fraction was purified to homogeneity and had a single polypeptide chain of 53 to 54 kilodaltons, with an isoelectric point of 8.1. Each enzyme was thermostable, the temperature optimum was 75 degrees C, and 30 mM NaCl, 1.5 M urea, or 0.004% sodium dodecyl sulfate caused 50% inhibition of the enzymes. However, 2% Triton X-100 did not have an inhibitory effect. The enzymes were also able to catalyze the reduction of sodium selenite and sodium sulfite in vitro. NADH was replaceable by NADPH. Divalent cations, such as Ca2+ and Ba2+, had no effect on the activity, while similar concentrations of Zn2+, Ni2+, and Cu2+ abolished the activity. This reductase activity could enable these bacteria both to reduce K2TeO3 and to increase their tolerance toward this salt.
嗜热栖热菌HB8的无细胞提取物可在体外催化依赖于NADH的亚碲酸钾（K2TeO3）还原反应。鉴定出了三种具有亚碲酸盐还原活性的不同蛋白质组分。其中两种表现出高分子量，且由至少两种不同的多肽组成。第三种组分中的蛋白质被纯化至同质，具有一条53至54千道尔顿的单多肽链，等电点为8. I。每种酶都具有热稳定性，最适温度为75摄氏度，30 mM氯化钠、1.5 M尿素或0.004%十二烷基硫酸钠可导致酶活性受到50%的抑制。然而，2% Triton X-100没有抑制作用。这些酶在体外也能够催化亚硒酸钠和亚硫酸钠的还原反应。NADH可被NADPH替代。二价阳离子，如Ca2+和Ba2+，对活性没有影响，而相似浓度的Zn2+、Ni2+和Cu2+会使活性丧失。这种还原酶活性可能使这些细菌既能还原K2TeO3，又能增强它们对这种盐的耐受性。
