Stouthamer A H
Faculty of Biology, Vrije Universiteit, Amsterdam, The Netherlands.
Antonie Van Leeuwenhoek. 1992 Jan;61(1):1-33. doi: 10.1007/BF00572119.
Denitrification and methylotrophy in Paracoccus denitrificans are discussed. The properties of the enzymes of denitrification: the nitrate-nitrite antiporter, nitrate reductase, nitrite reductase, nitric oxide reductase and nitrous oxide reductase are described. The genes for none of these proteins have yet been cloned and sequenced from P. denitrificans. A number of sequences are available for enzymes from Escherichia coli, Pseudomonas stutzeri and Pseudomonas aeruginosa. It is concluded that pathway specific c-type cytochromes are involved in denitrification. At least 40 genes are involved in denitrification. In methanol oxidation at least 20 genes are involved. In this case too pathway specific c-type cytochromes are involved. The sequence homology between the quinoproteins methanol dehydrogenase, alcoholde-hydrogenase and glucose dehydrogenase is discussed. This superfamily of proteins is believed to be derived from a common ancestor. The moxFJGI operon determines the structural components of methanol dehydrogenase and the associated c-type cytochrome. Upstream of this operon 3 regulatory proteins were found. The moxY protein shows the general features of a sensor protein and the moxX protein those of a regulatory protein. Thus a two component regulatory system is involved in both denitrification and methylotrophy. The phylogeny of prokaryotes based on 16S rRNA sequence is discussed. It is remarkable that the 16S rRNA of Thiosphaera pantotropha is identical to that of P. denitrificans. Still these bacteria show a number of differences. T. pantotropha is able to denitrify under aerobic circumstances and it shows heterotrophic nitrification. Nitrification and heterotrophic nitrification are found in species belonging to the beta-and gamma-subdivisions of purple non-sulfur bacteria. Thus the occurrence of heterotrophic nitrification in T. pantotropha, which belongs to the alpha-subdivision of purple non-sulfur bacteria is a remarkable property. Furthermore T. pantotropha contains two nitrate reductases of which the periplasmic one is supposed to be involved in aerobic denitrification. The nitrite reductase is of the Cu-type and not of the cytochrome cd1 type as in P. denitrificans. Also the cytochrome b of the Qbc complex of T. pantotropha is highly similar to its counterpart in P. denitrificans. It is hypothesized that the differences between these two organisms which both contain large megaplasmids is due to a combination of loss of genetic information and plasmid-coded properties. The distribution of a number of complex metabolic systems in eubacteria and in a number of species belonging to the alpha-group of purple non sulphur bacteria is reviewed.(ABSTRACT TRUNCATED AT 400 WORDS)
本文讨论了反硝化副球菌中的反硝化作用和甲基营养作用。描述了反硝化作用相关酶的特性：硝酸盐-亚硝酸盐反向转运蛋白、硝酸盐还原酶、亚硝酸盐还原酶、一氧化氮还原酶和一氧化二氮还原酶。目前尚未从反硝化副球菌中克隆和测序这些蛋白质的基因。大肠杆菌、施氏假单胞菌和铜绿假单胞菌中这些酶的一些序列是已知的。得出的结论是，途径特异性的c型细胞色素参与反硝化作用。至少有40个基因参与反硝化作用。在甲醇氧化过程中，至少有20个基因参与。在这种情况下，同样有途径特异性的c型细胞色素参与。讨论了醌蛋白甲醇脱氢酶、醇脱氢酶和葡萄糖脱氢酶之间的序列同源性。这个蛋白质超家族被认为起源于一个共同的祖先。moxFJGI操纵子决定了甲醇脱氢酶和相关c型细胞色素的结构成分。在这个操纵子上游发现了3种调节蛋白。moxY蛋白具有传感蛋白的一般特征，moxX蛋白具有调节蛋白的特征。因此，一个双组分调节系统参与了反硝化作用和甲基营养作用。讨论了基于16S rRNA序列的原核生物系统发育。值得注意的是，泛养硫球菌的16S rRNA与反硝化副球菌的相同。然而，这些细菌仍存在一些差异。泛养硫球菌能够在有氧条件下进行反硝化作用，并表现出异养硝化作用。硝化作用和异养硝化作用在紫色非硫细菌的β-和γ-亚类物种中存在。因此，属于紫色非硫细菌α-亚类的泛养硫球菌中出现异养硝化作用是一个显著的特性。此外，泛养硫球菌含有两种硝酸盐还原酶，其中周质中的那种被认为参与有氧反硝化作用。其亚硝酸盐还原酶是铜型的，而不是像反硝化副球菌那样是细胞色素cd1型的。泛养硫球菌Qbc复合物的细胞色素b也与其在反硝化副球菌中的对应物高度相似。据推测，这两种都含有大型大质粒的生物体之间的差异是由于遗传信息的丢失和质粒编码特性的综合作用。综述了一些复杂代谢系统在真细菌和一些属于紫色非硫细菌α-群的物种中的分布。（摘要截短于400字）
