Enzymatic properties of Myxococcus xanthus exopolyphosphatases mxPpx1 and mxPpx2
| Autor: | Daiki Harita, Kousei Kanie, Yoshio Kimura |
|---|---|
| Rok vydání: | 2021 |
| Předmět: |
Myxococcus xanthus
GTP' Phosphatase Biophysics Biochemistry Pyrophosphate Substrate Specificity Analytical Chemistry 03 medical and health sciences chemistry.chemical_compound Bacterial Proteins ATP hydrolysis Guanosine pentaphosphate Molecular Biology 030304 developmental biology Exopolyphosphatase chemistry.chemical_classification 0303 health sciences biology 030306 microbiology Hydrolysis Guanosine Pentaphosphate biology.organism_classification Phosphoric Monoester Hydrolases Acid Anhydride Hydrolases Kinetics Enzyme chemistry |
| Zdroj: | Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics. 1869:140660 |
| ISSN: | 1570-9639 |
| DOI: | 10.1016/j.bbapap.2021.140660 |
| Popis: | Myxococcus xanthus possesses two exopolyphosphatases, mxPpx1 and mxPpx2, which belong to the family of Ppx/GppA phosphatases; however, their catalytic properties have not been described. mxPpx1 and mxPpx2 contain 311 and 505 amino acid residues, respectively; mxPpx2 has an additional C-terminal region, which corresponds to the metal-dependent HDc phosphohydrolase domain. mxPpx1 mainly hydrolyzed short-chain polyPs (polyP3 and polyP4), whereas mxPpx2 preferred long-chain polyP60–70 and polyP700–1000. mxPpx2 was activated by 25–50 mM KCl, but mxPpx1 did not significantly depend on K+. In addition, mxPpx1 and mxPpx2 showed weak hydrolysis of ATP and GTP in the absence of K+, and mxPpx2 could also hydrolyze guanosine pentaphosphate (pppGpp) in the presence of K+. The exopolyphosphatase activity of mxPpx1 toward polyP3 was inhibited by polyP700–1000 and that of mxPpx2 toward polyP60–70 and polyP700–1000, by pyrophosphate. To clarify the function of the mxPpx2 C-terminal domain, it was fused to mxPpx1 (mxPpx1-2C) and deleted from mxPpx2 (mxPpx2∆C). Compared to wild-type mxPpx2, mxPpx2∆C had significantly reduced exopolyphosphatase activity toward long-chain polyPs (by 90%), whereas that toward polyP3 and polyP4 was much less affected; furthermore, the phosphohydrolase activity toward pppGpp, ATP, and GTP was also decreased (by 30–75%). In contrast, mxPpx1-2C had increased hydrolytic activity compared to mxPpx1. Furthermore, mxPpx2∆C lost the requirement for K+ characteristic for the wild-type enzyme, whereas mxPpx1-2C acquired it. These results suggest that the C-terminal domain of mxPpx2 is necessary for its maximum hydrolytic activity, especially toward long-chain polyPs, and defines mxPpx2 dependency on K+ for activation. |
| Databáze: | OpenAIRE |
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