Ascaris suum cytochrome b5, an adult-specific secretory protein reducing oxygen-avid ferric hemoglobin

The anaerobic parasitic nematode Ascaris suum has an oxygen-avid hemoglobin in the perienteric fluid, the biological function of which remains elusive. Here, we report that Ascaris cytochrome b5 is expressed specifically in the intestinal parasitic stage and is secreted into the perienteric fluid, t...

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Bibliographic Details
Published in:Archives of biochemistry and biophysics 2008-03, Vol.471 (1), p.42-49
Main Authors: Hashimoto, Muneaki, Takamiya, Shinzaburo, Yokota, Takehiro, Nakajima, Yoshitaka, Yamakura, Fumiyuki, Sugio, Shigetoshi, Aoki, Takashi
Format: Article
Language:English
Subjects:
Anaerobiosis
Animals
Ascaris suum - enzymology
Ascaris suum - growth & development
Body Fluids - enzymology
Cytochromes b5 - chemistry
Cytochromes b5 - physiology
Cytochromes b5 - secretion
Ferric Compounds - metabolism
Ferrous Compounds - metabolism
Humans
Methemoglobin - metabolism
Oxidation-Reduction
Oxygen - metabolism
Protein Binding
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Summary:The anaerobic parasitic nematode Ascaris suum has an oxygen-avid hemoglobin in the perienteric fluid, the biological function of which remains elusive. Here, we report that Ascaris cytochrome b5 is expressed specifically in the intestinal parasitic stage and is secreted into the perienteric fluid, thus co-localizing with Ascaris hemoglobin. We also found that cytochrome b5 reduces Ascaris non-functioning ferric methemoglobin more efficiently than mammalian methemoglobin. Furthermore, a computer graphics model of the electron transfer complex between Ascaris cytochrome b5 and Ascaris hemoglobin strongly suggested that these two proteins are physiological redox partners. Nitric oxide has been reported to react easily with oxygen captured in hemoglobin to form nitrate, but not toxic free radicals, which may result in production of methemoglobin for the cytochrome b5 to regenerate functional ferrous hemoglobin. Therefore, our findings suggest that Ascaris cytochrome b5 is a key redox partner of Ascaris hemoglobin, which acts as an antioxidant.
ISSN:0003-9861
1096-0384
DOI:10.1016/j.abb.2007.12.003