Yumoto N, Tokushige M
Department of Chemistry, Faculty of Science, Kyoto University, Japan.
Biochem Biophys Res Commun. 1988 Jun 30;153(3):1236-43. doi: 10.1016/s0006-291x(88)81360-3.
Two different types of fumarase were found in sonic extracts of Escherichia coli; one required Fe-S for the enzyme activity, and the other did not. When the cells were grown without aeration, the Fe-S-independent enzyme occupied over 80% of the overall fumarase activity. Highly purified Fe-S-independent enzyme was suggested to be composed of four subunits (Mr = 48 kDa) by SDS-polyacrylamide gel electrophoresis and gel filtration. Amino acid and N-terminal sequence analyses supported the possibility that the enzyme is a product of fumC gene (FUMC). In aerobically grown cells, however, the content of FUMC was low and the Fe-S-dependent fumarase occupied over 80% of the overall activity. The Fe-S-dependent enzyme appeared to be labile and the activity was rapidly lost during purification. Although the spontaneous inactivation was previously ascribed to thermal lability (S.A. Woods & J.R. Guest (1987) FEMS Microbiol. Lett. 48, 219), the activity could be restored by anaerobic incubation with ferrous ions and SH-compounds.
在大肠杆菌的超声提取物中发现了两种不同类型的延胡索酸酶；一种酶活性需要铁硫簇，另一种则不需要。当细胞在无通气条件下生长时，不依赖铁硫簇的酶占总延胡索酸酶活性的80%以上。通过SDS-聚丙烯酰胺凝胶电泳和凝胶过滤表明，高度纯化的不依赖铁硫簇的酶由四个亚基（Mr = 48 kDa）组成。氨基酸和N端序列分析支持该酶是fumC基因（FUMC）产物的可能性。然而，在需氧生长的细胞中，FUMC的含量较低，依赖铁硫簇的延胡索酸酶占总活性的80%以上。依赖铁硫簇的酶似乎不稳定，在纯化过程中活性迅速丧失。尽管之前自发失活被归因于热不稳定性（S.A. Woods和J.R. Guest（1987年），FEMS Microbiol. Lett. 48, 219），但通过与亚铁离子和硫氢化合物进行厌氧孵育，活性可以恢复。
