Open AccessCharacterization of a soluble catalase‐peroxidase hemoprotein b ‐590, previously identified as ‘cytochrome a 1 ’ from Bradyrhizobium japonicum bacteroids
Author(s) -
Appleby Cyril A.,
Poole Robert K.
Publication year - 1991
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.1991.tb04464.x
Subject(s) - bradyrhizobium japonicum , leghemoglobin , hemeprotein , heme , bradyrhizobium , peroxidase , chemistry , dithionite , catalase , cytochrome c peroxidase , rhizobium , biochemistry , nitrogenase , oxidase test , cytochrome c oxidase , cytochrome , nitrogen fixation , rhizobiaceae , biology , enzyme , bacteria , symbiosis , nitrogen , root nodule , organic chemistry , genetics , gene
Summary The cytochrome “ a 1 ” or P‐428, previously proposed to be a high affinity terminal oxidase in nitrogen‐fixing bacteroids of Bradyrhizobium japonicum has been purified. The water‐soluble native hemoprotein has an M r of 136 000, lacks heme a and is a high‐spin ferric protohemoprotein: It is slowly reduced with dithionite to give a species with an optical spectrum like that of hemoprotein b ‐590 ( Escherichia coli ; peak at 555 nm, shoulder at 590 nm), and which reacts slowly with CO. It has catalase and peroxidase activities, again resembling the E. colib ‐590. Neither hemoprotein forms a stable oxy complex under conditions in which dithionite‐reduced horseradish per‐oxidase reacts with oxygen to form such a complex. The hemoprotein, which we name hemoprotein, b ‐590 ( Bradyrhizobium japonicum , may play a role in removal of peroxides generated during respiration in the bacteroids of several Rhizobium and Bradyrhizobium species. The high‐affinity terminal oxidase under nitrogen‐fixing conditions remains to be identified.