Characterization of a soluble catalase-peroxidase hemoprotein b-590, previously identified as 'cytochrome alpha 1' from Bradyrhizobium japonicum bacteroids.
The cytochrome "a1" 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 Mr 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. coli b-590. Neither hemoprotein forms a stable oxy complex under conditions in which dithionite-reduced horseradish peroxidase 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.
Appleby
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CA
Division of Plant Industry, CSIRO, Canberra, Australia.
Poole
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D002374:Catalase / Q000378:metabolism; D003580:Cytochromes / Q000302:isolation & purification / Q000378:metabolism; D045263:Cytochromes a1; D006420:Hemeproteins / Q000302:isolation & purification* / Q000378:metabolism; D009195:Peroxidase / Q000378:metabolism; D012230:Rhizobiaceae / Q000201:enzymology*; D012995:Solubility; D013057:Spectrum Analysis
D003580:Cytochromes; D006420:Hemeproteins; D045263:Cytochromes a1; D002374:Catalase; D009195:Peroxidase