硫氧还蛋白(Trx)是一种含二硫化物的氧化还原蛋白,其作为二硫化物氧化还原酶起作用。黄毒粘球菌含有5个Trxs(Trx1-Trx5)和1个Trx还原酶(TrxR)。Trxs通常具有CGPC活性位点基序;然而,黄花M.Trxs的活性位点序列略有不同,除了Trx4。黄药的五个Trxs表现出降低的抗胰岛素活性,5,5'-二硫代双(2-硝基苯甲酸)(DTNB),胱氨酸,谷胱甘肽二硫化物(GSSG),S-亚硝基谷胱甘肽(GSNO),和H2O2在TrxR的存在下。黄药腺苷酸激酶和丝氨酸/苏氨酸磷酸酶活性,通过添加二硫苏糖醇而增加,通过添加Trxs和TrxR激活。其中,Trx1在其活性位点有一个CAPC序列,除GSNO外,还原活性最高。黄花M.TrxR对DTNB的还原活性较弱,GSSG,GSNO,和H2O2,表明它具有广泛的底物特异性,与以前报道的低分子量TrxRs不同。以TrxR还原氧化Trx1为最佳底物,kcat/Km值为0.253min-1μM-1,比其他Trxs高10-28倍。这些结果表明,所有Trxs都具有还原活性,并且Trxl在黄菊中可能是功能最强的,因为TrxR最有效地还原氧化的Trxl。
Thioredoxin (Trx) is a disulfide-containing redox protein that functions as a disulfide oxidoreductase. Myxococcus xanthus contains five Trxs (Trx1-Trx5) and one Trx reductase (TrxR). Trxs typically have a CGPC active-site motif; however, M. xanthus Trxs have slightly different active-site sequences, with the exception of Trx4. The five Trxs of M. xanthus exhibited reduced activities against insulin, 5,5\'-dithiobis(2-nitrobenzoic acid) (DTNB), cystine, glutathione disulfide (GSSG), S-nitrosoglutathione (GSNO), and H2O2 in the presence of TrxR. Myxococcus xanthus adenylate kinase and serine/threonine phosphatase activities, which were increased by the addition of dithiothreitol, were activated by the addition of Trxs and TrxR. Among these, Trx1, which has a CAPC sequence in its active site, exhibited the highest reducing activity with the exception of GSNO. Myxococcus xanthus TrxR showed weak reducing activity towards DTNB, GSSG, GSNO, and H2O2, suggesting that it has broad substrate specificity, unlike previously reported low-molecular-weight TrxRs. TrxR reduced oxidized Trx1 as the best substrate, with a kcat/Km value of 0.253 min-1 µM-1, which was 10-28-fold higher than that of the other Trxs. These results suggest that all Trxs possess reducing activity and that Trx1 may be the most functional in M. xanthus because TrxR most efficiently reduces oxidized Trx1.