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Tartrate-resistant acid phosphatase 5B circulates in human serum in complex with alpha2-macroglobulin and calcium |
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| Authors: | Ylipahkala Hannele Halleen Jussi M Kaija Helena Vihko Pirkko Väänänen H Kalervo |
| Affiliation: | a Department of Anatomy, Institute of Biomedicine, University of Turku, 20520 Turku, Finland b Biocenter Oulu and Research Center for Molecular Endocrinology, University of Oulu, Oulu, Finland |
| Abstract: | Tartrate-resistant acid phosphatase (TRACP) is an enzyme with unknown biological function. In addition to its acid phosphatase activity, TRACP is capable of generating reactive oxygen species (ROS) at neutral pH. Two forms of TRACP circulate in human serum, macrophage-derived TRACP 5a and osteoclast-derived TRACP 5b. Here we have studied the circulating forms of the osteoclast-derived TRACP 5b in rat and human serum. In human serum, TRACP 5b circulates in a large complex that contained α2M and calcium. On the contrary, rat serum TRACP 5b circulates as a free molecule. Formation of the TRACP 5b complex in vitro decreased significantly the ROS generating activity of TRACP 5b without affecting its phosphatase activity. These results suggest that the complex formation may be necessary to eliminate the formation of the harmful ROS in the neutral pH of serum. |
| Keywords: | TRACP 5b Serum complex α2-Macroglobulin Calcium Osteoclast |
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