Zarzycki Jan, Schlichting Ansgar, Strychalsky Nina, Müller Michael, Alber Birgit E, Fuchs Georg
Mikrobiologie, Fakultät für Biologie, Universität Freiburg, Germany.
J Bacteriol. 2008 Feb;190(4):1366-74. doi: 10.1128/JB.01621-07. Epub 2007 Dec 7.
The coenzyme A (CoA)-activated C5-dicarboxylic acids mesaconyl-CoA and beta-methylmalyl-CoA play roles in two as yet not completely resolved central carbon metabolic pathways in bacteria. First, these compounds are intermediates in the 3-hydroxypropionate cycle for autotrophic CO2 fixation in Chloroflexus aurantiacus, a phototrophic green nonsulfur bacterium. Second, mesaconyl-CoA and beta-methylmalyl-CoA are intermediates in the ethylmalonyl-CoA pathway for acetate assimilation in various bacteria, e.g., in Rhodobacter sphaeroides, Methylobacterium extorquens, and Streptomyces species. In both cases, mesaconyl-CoA hydratase was postulated to catalyze the interconversion of mesaconyl-CoA and beta-methylmalyl-CoA. The putative genes coding for this enzyme in C. aurantiacus and R. sphaeroides were cloned and heterologously expressed in Escherichia coli, and the proteins were purified and studied. The recombinant homodimeric 80-kDa proteins catalyzed the reversible dehydration of erythro-beta-methylmalyl-CoA to mesaconyl-CoA with rates of 1,300 micromol min(-1) mg protein(-1). Genes coding for similar enzymes with two (R)-enoyl-CoA hydratase domains are present in the genomes of Roseiflexus, Methylobacterium, Hyphomonas, Rhodospirillum, Xanthobacter, Caulobacter, Magnetospirillum, Jannaschia, Sagittula, Parvibaculum, Stappia, Oceanicola, Loktanella, Silicibacter, Roseobacter, Roseovarius, Dinoroseobacter, Sulfitobacter, Paracoccus, and Ralstonia species. A similar yet distinct class of enzymes containing only one hydratase domain was found in various other bacteria, such as Streptomyces species. The role of this widely distributed new enzyme is discussed.
辅酶A（CoA）激活的C5 - 二羧酸中康酰辅酶A和β - 甲基苹果酰辅酶A在细菌中两条尚未完全解析的中心碳代谢途径中发挥作用。首先，这些化合物是嗜热栖热放线菌（一种光合绿色非硫细菌）中自养二氧化碳固定的3 - 羟基丙酸循环的中间体。其次，中康酰辅酶A和β - 甲基苹果酰辅酶A是各种细菌（如球形红杆菌、扭脱甲基杆菌和链霉菌属）中乙酸同化的乙基丙二酰辅酶A途径的中间体。在这两种情况下，推测中康酰辅酶A水合酶催化中康酰辅酶A和β - 甲基苹果酰辅酶A的相互转化。在嗜热栖热放线菌和球形红杆菌中编码该酶的假定基因被克隆并在大肠杆菌中进行异源表达，然后对蛋白质进行纯化和研究。重组的同型二聚体80 kDa蛋白质催化赤藓糖型β - 甲基苹果酰辅酶A可逆脱水生成中康酰辅酶A，速率为1300 μmol min⁻¹ mg蛋白质⁻¹。编码具有两个（R） - 烯酰辅酶A水合酶结构域的类似酶的基因存在于玫瑰弯菌属、甲基杆菌属、生丝单胞菌属、红螺菌属、黄色杆菌属、柄杆菌属、嗜磁螺菌属、詹氏菌属、箭形菌属、短小杆菌属、斯塔皮亚菌属、海栖菌属、洛氏菌属、硅细菌属、玫瑰杆菌属、玫瑰微球菌属、海氏玫瑰杆菌属、亚硫酸杆菌属、副球菌属和雷尔氏菌属的基因组中。在各种其他细菌（如链霉菌属）中发现了一类类似但不同的仅含有一个水合酶结构域的酶。本文讨论了这种广泛分布的新酶的作用。
