McTavish H, Fuchs J A, Hooper A B
Department of Genetics and Cell Biology, University of Minnesota, St. Paul 55108.
J Bacteriol. 1993 Apr;175(8):2436-44. doi: 10.1128/jb.175.8.2436-2444.1993.
Nitrosomonas europaea, a chemolithotrophic bacterium, was found to contain two copies of the gene coding for the presumed active site polypeptide of ammonia monooxygenase, the 32-kDa acetylene-binding polypeptide. One copy of this gene was cloned, and its complete nucleotide sequence is presented. Immediately downstream of this gene, in the same operon, is the gene for a 40-kDa polypeptide that copurifies with the ammonia monooxygenase acetylene-binding polypeptide. The sequence of the first 692 nucleotides of this structural gene, coding for about two-thirds of the protein, is presented. These sequences are the first sequences of protein-encoding genes from an ammonia-oxidizing autotrophic nitrifying bacterium. The two protein sequences are not homologous with the sequences of any other monooxygenase. From radioactive labelling of ammonia monooxygenase with [14C]acetylene it was determined that there are 23 nmol of ammonia monooxygenase per g of cells. The kcat of ammonia monooxygenase for NH3 in vivo was calculated to be 20 s-1.
欧洲亚硝化单胞菌是一种化能自养细菌，被发现含有编码氨单加氧酶假定活性位点多肽（32 kDa乙炔结合多肽）的基因的两个拷贝。该基因的一个拷贝被克隆，并给出了其完整的核苷酸序列。在同一操纵子中，该基因的紧邻下游是一个与氨单加氧酶乙炔结合多肽共纯化的40 kDa多肽的基因。给出了该结构基因前692个核苷酸的序列，其编码约三分之二的蛋白质。这些序列是来自氨氧化自养硝化细菌的蛋白质编码基因的首批序列。这两个蛋白质序列与任何其他单加氧酶的序列均无同源性。通过用[14C]乙炔对氨单加氧酶进行放射性标记，确定每克细胞中有23 nmol氨单加氧酶。体内氨单加氧酶对NH3的催化常数（kcat）经计算为20 s-1。
