TAILIEUCHUNG - Báo cáo khóa học: Trypanosoma brucei oleate desaturase may use a cytochrome b5-like domain in another desaturase as an electron donor

An open reading frame with fatty acid desaturase similarity was identified in the genome ofTrypanosoma 1224 bp sequence specifies a proteinof 408 amino acids with 59% and 58% similarity toMortierella alpinaandArabid-opsis thalianaD12 desaturase, respectively, and 51% with A. thalianax3 desaturases. The histidine tracks that com-pose the iron-binding active centers of the enzyme were more similar to those of thex3 desaturases. | Eur. J. Biochem. 271 1079-1086 2004 FEBS 2004 doi Trypanosoma brucei oleate desaturase may use a cytochrome b5-like domain in another desaturase as an electron donor Guillermo A. Petrini Silvia G. Altabe and Antonio D. Uttaro Instituto de Biologia Molecular y Celular de Rosario IBR CONICET Departamento de Microbiologia Facultad de Ciencias Bioquimicas y Farmaceuticas Universidad Nacional de Rosario Santa Fe Argentina An open reading frame with fatty acid desaturase similarity was identified in the genome of Trypanosoma brucei. The 1224 bp sequence specifies a protein of408 amino acids with 59 and 58 similarity to Mortierella alpina and Arabid-opsis thaliana A12 desaturase respectively and 51 with A. thaliana 3 desaturases. The histidine tracks that compose the iron-binding active centers of the enzyme were more similar to those of the 1 3 desaturases. Expression of the trypanosome gene in Saccharomyces cerevisiae resulted in the production of fatty acids that are normally not synthesized in yeast namely linoleic acid 18 2A9 12 and hexadecadienoic acid 16 2A9 12 the levels of which were dependent on the culture temperature. At low temperature the production of bi-unsaturated fatty acids and the 16 2 18 2 ratio were higher. Transformed yeast cultures supplemented with 19 1A10 fatty acid yielded 19 2A10 13 indicating that the enzyme is able to introduce a double bond at three carbon atoms from a pre-existent olefinic bond. The expression of the gene in a S. cerevisiae mutant defective in cytochrome b5 showed a significant reduction in bi-unsat-urated fatty acid production although it was not totally abolished. Based on the regioselectivity and substrate preferences we characterized the trypanosome enzyme as a cytochrome b5-dependent oleate desaturase. Expression of the ORF in a double mutant ole1A cytb5A abolished all oleate desaturase activity completely. OLE1 codes for the endogenous stearoyl-CoA desaturase. Thus Ole1p has like .

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