Leishmania Major Encodes an Unusual Peroxidase That is a Close Homologue of Plant Ascorbate Peroxidase: A Novel Role of the Transmembrane Domain
IR@IICB: CSIR-Indian Institute of Chemical Biology, Kolkata
View Archive Info| Field | Value | |
| Title |
Leishmania Major Encodes an Unusual Peroxidase That is a Close Homologue of Plant Ascorbate Peroxidase: A Novel Role of the Transmembrane Domain
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| Creator |
Adak, Subrata
Dutta, Alok K |
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| Subject |
Infectious Diseases and Immunology
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| Description |
Haem-containing enzymes (peroxidase and catalase) are widely
distributed among prokaryotes and eukaryotes and play a vital role inH2O2 detoxification. But, to date, no haem-containing enzymatic defence against toxic H2O2 has been discovered in Leishmania species. We cloned, expressed and purified an unusual plant-like APX (ascorbate peroxidase) from Leishmania major (LmAPX) and characterized its catalytic parameters under steady-state conditions. Examination of its protein sequence indicated approx.
30–60% identity with other APXs. The N-terminal extension
of LmAPX is characterized by a charged region followed by a
stretch of 22 amino acids containing a transmembrane domain.
To understand how the transmembrane domain influences the
structure–function of LmAPX, we generated, purified and extensively characterized a variant that lacked the transmembrane domain. Eliminating the transmembrane domain had no impact on substrate-binding affinity but slowed down ascorbate oxidation and increased resistance to H2O2-dependent inactivation in the absence of electron donor by 480-fold. Spectral studies show that H2O2 can quickly oxidize the native enzyme to compound (II), which subsequently is reduced back to the native enzyme by an
electron donor. Incontrast, ascorbate-free transmembrane domaincontaining enzyme did not react with H2O2, as revealed by the absence of compound (II) formation. Our findings suggest that the single copy LmAPX gene may play an important role in detoxification of H2O2 that is generated by endogenous processes and as a result of external influences such as the oxidative burst
of infected host macrophages or during drug metabolism by
Leishmania.
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| Date |
2005
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| Type |
Article
PeerReviewed |
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| Format |
application/pdf
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| Identifier |
http://www.eprints.iicb.res.in/332/1/BIOCHEMICAL_JOURNAL_390_465%2D%E0%A4%9B2005%E0%A4%A131%E0%A4%BC.pdf
Adak, Subrata and Dutta, Alok K (2005) Leishmania Major Encodes an Unusual Peroxidase That is a Close Homologue of Plant Ascorbate Peroxidase: A Novel Role of the Transmembrane Domain. Biochemical Journal, 390. pp. 465-474. |
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| Relation |
http://dx.doi.org/10.1042/BJ20050311
http://www.eprints.iicb.res.in/332/ |
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