Cytochrome c-557 (551) and cytochrome cd of Alcaligenes faecalis

1. Cytochrome c-557 (551) was prepared from Alcaligenes faecalis. The molecular weight was 65,000. The haem groups were not split off by the ordinary acid-acetone treatment and, in the presence of pyridine, a normal c-type haemochrome was formed. The cytochrome was found to be a dihaem protein. The reduced form of this cytochrome reacted with CO and the oxidized one with cyanide at pH 7. 2. A two-haem cytochrome (cytochrome cd) was crystallized from the same organism. The molecular weight was 90,000. This cytochrome contained a c-type haem and a tf-like haem, and two atoms of iron per molecule. The c-haem seems to be re-sponsible for its typical a peak with a shoulder. The rf-like haem reacted with CO, CN", NO2 " and NO under different conditions. Cytochrome cd had a strong nitrite reductase activity. 3. This microorganism had a strong denitrifying activity in anaerobic condition. The cytochrome c-557 (551) was present in the cells grown in the absence of nitrate and nitrite, whereas the cytochrome cd and a small quantity of cytochrome c-557 (551) were present in the cells grown in the presence of nitrate or nitrite. Both cytochromes were absent in the cells grown under high aeration. Haemoproteins of Alcaligenes faecalis were, ex- stutzeri (5). amined in the present study. In a soluble This paper describes the method of puri-fraction of the cells grown in a KNO3-free fication and the characteristics of these haemo-medium, cytochrome c-557 (551) with absorp- proteins. It was deduced from the results tion spectra similar to cytochrome c-552, 558 that cytochrome cd acts as a nitrite reductase of Pseudomonas stutzeri ( / ) was found while in a dissimilatory nitrite reduction. The con-a crf-type cytochrome was found in a soluble ditions under which they are synthesized are fraction of the cells grown in the presence of also described. nitrate. The latter haemoprotein resembled, in spectral properties, the cd-type cytochrome MATERIALS AND METHODS of various denitrifying bacteria; Pseudomona