Open AccessHeme P460 of Hydroxylamine Oxidoreductase of Nitrosomonas
Author(s) -
HOOPER Alan B.,
DEBEY Pascale,
ANDERSSON Kristoffer K.,
BALNY Claude
Publication year - 1983
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1983.tb07534.x
Subject(s) - chemistry , ferrous , hydroxylamine , heme , nitrosomonas europaea , dehydrogenation , nitrosomonas , photochemistry , medicinal chemistry , oxidoreductase , nitrite , globin , stereochemistry , inorganic chemistry , hemoglobin , organic chemistry , catalysis , enzyme , nitrate
Hydroxylamine oxidoreductase (HAO) of Nitrosomonas catalyzes the dehydrogenation of NH 2 OH and subsequent addition of oxygen to form nitrite. HAO contains c hemes and the CO‐binding heme P460 in a 7:1 ratio; dehydrogenation of NH 2 OH involves passage of electrons to P460 and then c hemes. We now report that electrons rapidly pass from c hemes of HAO to the P460 center and then to H 2 O 2 . This conclusion is supported by (a) inhibition of c heme oxidation with CO and (b) loss of H 2 O 2 ‐oxidizability of ferrous c hemes following specific destruction of heme P460. Reaction of ferrous P460 with H 2 O 2 is rate‐limiting. Activation of dioxygen for N‐oxidation by ferrous HAO may involve the two‐electron reduction of O 2 by P460. The reaction of ferrous HAO with H 2 O 2 was studied as it may reveal aspects of the mechanism of activation of dioxygen. Reaction of ferrous heme P460 with CO is slow and with low affinity as compared with other hemoproteins. Values for reaction of CO with enzyme were: k 1 , 1.1 × 10 −3 M −1 s −1 and K d , 12μM.