Publication Date:
2014-06-26
Description:
Leishmania major was proposed to either utilize heme from its host or partially synthesize the tetrapyrrole from host provided precursors. However, only indirect evidence was available for this partial late heme biosynthetic pathway. Here, we demonstrate that the LMJF_06_1280 gene of L. major encodes a HemG-type protoporphyrinogen IX oxidase catalyzing the oxidation of protoporphyrinogen IX to protoporphyrin IX. Interestingly, trypanosomatids are currently the only known eukaryotes possessing HemG-type enzymes. The LMJF_06_1280 gene forms a potential transcriptional unit with LMJF_06_1270 encoding coproporphyrinogen III oxidase and with LMJF_06_1290 for a cytochrome b 5 . In vivo function of the L. major hemG gene was shown by the functional complementation of the E. coli ΔhemG strain LG285. Restored heme formation in E. coli was observerd using HPLC analyses. Purified recombinant L. major HemG revealed protoporphyrinogen IX oxidase activity in vitro using different ubiquinones and triphenyltetrazolium as electron acceptors. FMN was identified as the L. major HemG cofactor. Active site residues were found to be essential for HemG catalysis. These data in combination with the solved crystal structures of L. major coproporphyrinogen III oxidase and the physiological proof of a ferrochelatase activity provide clear-cut evidence for a partial heme biosynthetic pathway in L. major.
Print ISSN:
0144-8463
Electronic ISSN:
1573-4935
Topics:
Biology
,
Chemistry and Pharmacology
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