BshB, a key enzyme in bacillithiol biosynthesis, hydrolyses the acetyl group from N-acetylglucosamine malate to generate glucosamine malate. In Bacillus anthracis, BA1557 has been identified as the N-acetylglucosamine malate deacetylase (BshB); however, a high content of bacillithiol (~70%) was still observed in the B. anthracis ∆BA1557 strain. Genomic analysis led to the proposal that another deacetylase could exhibit cross-functionality in bacillithiol biosynthesis. In the present study, BA1557, its paralogue BA3888 and orthologous Bacillus cereus enzymes BC1534 and BC3461 have been characterized for their deacetylase activity towards N-acetylglucosamine malate, thus providing biochemical evidence for this proposal. In addition, the involvement of deacetylase enzymes is also expected in bacillithiol-detoxifying pathways through formation of S-mercapturic adducts. The kinetic analysis of bacillithiol-S-bimane conjugate favours the involvement of BA3888 as the B. anthracis bacillithiol-S-conjugate amidase (Bca). The high degree of specificity of this group of enzymes for its physiological substrate, along with their similar pH–activity profile and Zn2+-dependent catalytic acid–base reaction provides further evidence for their cross-functionalities.
BshB 是杆菌硫醇生物合成过程中的一种关键酶,它水解 N-乙酰氨基葡萄糖苹果酸盐中的乙酰基,生成氨基葡萄糖苹果酸盐。在炭疽芽孢杆菌(Bacillus anthracis)中,BA1557 已被确定为 N-乙酰葡糖胺苹果酸盐脱乙酰酶(BshB);然而,在炭疽芽孢杆菌 ∆BA1557 菌株中仍然观察到较高含量的杆菌硫醇(约 70%)。基因组分析结果表明,另一种脱乙酰酶可能在枯草硫酚的生物合成过程中表现出交叉功能。在本研究中,BA1557、其旁系亲属 BA3888 以及蜡样芽孢杆菌的直向同源酶 BC1534 和 BC3461 对 N-乙酰氨基葡萄糖苹果酸盐的脱乙酰酶活性进行了鉴定,从而为这一提议提供了生物化学证据。此外,预计脱乙酰酶还会通过形成 S-巯基加合物参与巴氏硫醇脱毒途径。杆菌硫醇-S-双烷共轭物的动力学分析表明,BA3888 是炭疽杆菌的杆菌硫醇-S-共轭物氨化酶(Bca)。这组酶对其生理底物的高度特异性,以及它们相似的 pH 活性曲线和 Zn2+ 依赖性催化酸碱反应,进一步证明了它们的跨功能性。