Molecular Characterization and Functional Analysis of Cytochrome b5 Reductase (CBR) Encoding Genes from the Carotenogenic XXXX Xanthophyllomyces dendrorhous.

@entity12364 @entity2125 @entity71222 @entity20467 @entity1110 @entity49650 @entity71223 @entity71224 @entity5068 @entity375
The eukaryotic microsomal cytochrome P450 systems consist of a cytochrome P450 enzyme (P450) and a cytochrome P450 redox partner, which generally is a cytochrome P450 reductase (CPR) that supplies electrons from @entity1110 . However, alternative electron donors may exist such as cytochrome b5 reductase and cytochrome b5 (CBR and @entity71222 , respectively) via, which is @entity2125 -dependent and are also anchored to the endoplasmic reticulum. In the carotenogenic @entity375 Xanthophyllomyces dendrorhous, three P450-encoding genes have been described: crtS is involved in carotenogenesis and the @entity49650 and @entity71223 genes are both implicated in @entity12364 biosynthesis. This @entity375 has a single CPR (encoded by the crtR gene), and a crtR- mutant does not produce @entity20467 . Considering that this mutant is viable, the existence of alternative cytochrome P450 electron donors like CBR and @entity71222 could operate in this @entity375 . The aim of this work was to characterize the X. dendrorhous CBR encoding gene and to study its involvement in P450 reactions in @entity12364 and carotenoid biosynthesis. Two CBRs genes were identified ( @entity71224 and CBR.2), and deletion mutants were constructed. The two mutants and the wild-type strain showed similar @entity5068 production, with @entity12364 being the main @entity5068 produced. The crtR- mutant strain produced a lower proportion of @entity12364 than did the parental strain. These results indicate that even though one of the two CBR genes could be involved in @entity12364 biosynthesis, crtR complements their absence in the cbr- mutant strains, at least for @entity12364 production. The higher @entity2125 -dependent cytochrome c reductase activity together with the higher transcript levels of @entity71224 and @entity71222 in the crtR- mutant as well as the lower @entity2125 -dependent activity in CBS- @entity71224 - strongly suggest that @entity71224 - @entity71222 via participates as an alternative electron donor pathway for P450 enzymes involved in @entity12364 biosynthesis in X. dendrorhous.
