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Journal of Immunology Research
Volume 2017, Article ID 7125084, 10 pages
https://doi.org/10.1155/2017/7125084
Research Article

Hemoglobins Likely Function as Peroxidase in Blood Clam Tegillarca granosa Hemocytes

1School of Marine Sciences, Ningbo University, Ningbo 315211, China
2Zhejiang Key Laboratory of Aquatic Germplasm Resources, Zhejiang Wanli University, Ningbo 315100, China

Correspondence should be addressed to Qinggang Xue; nc.ude.uwz@euxq and Yongbo Bao; moc.liamg@1002oabbob

Received 26 October 2016; Accepted 22 December 2016; Published 15 January 2017

Academic Editor: Yang Zhang

Copyright © 2017 Sufang Wang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Hemoglobins are a group of respiratory proteins principally functioning in transport of oxygen and carbon dioxide in red blood cells of all vertebrates and some invertebrates. The blood clam T. granosa is one of the few invertebrates that have hemoglobin-containing red hemocytes. In the present research, the peroxidase activity of T. granosa hemoglobins (Tg-Hbs) was characterized and the associated mechanism of action was deciphered via structural comparison with other known peroxidases. We detected that purified Tg-Hbs catalyzed the oxidation of phenolic compounds in the presence of exogenous H2O2. Tg-Hbs peroxidase activity reached the maximum at pH 5 and 35°C and was inhibited by Fe2+, Cu2+, SDS, urea, and sodium azide. Tg-Hbs shared few similarities in amino acid sequence and overall structural characteristics with known peroxidases. However, the predicted structure at their heme pocket was highly similar to that of horseradish peroxidase (HRP) and myeloperoxidase (MPO). This research represented the first systemic characterization of hemoglobin as a peroxidase.