The enzyme, characterized from plants, catalyses the hydroxylation of carbon 2 of long- or very-long-chain fatty acids attached to sphinganine during de novo ceramide synthesis. The enzyme requires an external cytochrome b5 as the electron donor. The newly introduced 2-hydroxyl group has R-configuration. cf. EC 188.8.131.52, 4-hydroxysphinganine ceramide fatty acyl 2-hydroxylase.
expression of Arabidopsis thaliana FAH1 gene, which does not contain the cytochrome b5 domain, in the Saccharomyces cerevisiae DELTAfah1 strain produces an approximately 25fold increase in alpha-hydroxyfatty acid 26:0 and reduces the levels of its 26-carbon precursor
Arabidopsis thaliana Bax inhibitor-1 -mediated suppression of cell death in yeast requires Saccharomyces cerevisiae fatty acid hydroxylase 1, which has a Cb5-like domain at the N terminus and interacts with Bax inhibitor-1
interaction with Arabidopsis cytochrome b5 is needed for sufficient activity. Isoform FAH1 mainly 2-hydroxylates very-long-chain fatty acids. In FAH1 knock-down lines, levels of hydroxylated fatty acids 22:0, 24:0, and 26:0 are considerably lower than in wild type, whereas the level of hydroxylated fatty acid 16:0 is marginally decreased. 2-Hydroxyfatty acids are related to resistance to oxidative stress, and isoform FAH1 or 2-hydroxy very-long-chain fatty acids show particularly strong responses to oxidative stress. Isoform FAH1 interacts with Bax inhibitor-1 via cytochrome b5 and is a key factor in Bax inhibitor-1-mediated cell death suppression; interaction with Arabidopsis cytochrome b5 is needed for sufficient activity. Isoform FAH2 selectively 2-hydroxylates palmitic acid in Arabidopsis. In FAH2 knock-down lines, the level of hydroxylated fatty acid 16:0 is reduced by 22.9%, whereas the levels of other 2-hydroxyfatty acids are similar to those in wild type
Arabidopsis thaliana FAH1 and FAH2 have no Cb5-like domain, and interact with electron transfer protein Cb5. Bax inhibitor-1 is a widely conserved cytoprotective protein localized in the endoplasmic reticulum membrane and also interacts with Cb5. Arabidopsis thaliana Bax inhibitor-1 -mediated suppression of cell death in yeast requires Saccharomyces cerevisiae fatty acid hydroxylase 1, which has a Cb5-like domain at the N terminus and interacts with Bax inhibitor-1
Fah1p, a Saccharomyces cerevisiae cytochrome b5 fusion protein, and its Arabidopsis thaliana homolog that lacks the cytochrome b5 domain both function in the alpha-hydroxylation of sphingolipid-associated very long chain fatty acids