Yeast Mpo1 Is a Novel Dioxygenase That Catalyzes the α-Oxidation of a 2-Hydroxy Fatty Acid in an Fe²⁺-Dependent Manner

ABSTRACT

Phytosphingosine (PHS) is the major long-chain base component of sphingolipids in Saccharomyces cerevisiae. The PHS metabolic pathway includes a fatty acid (FA) α-oxidation reaction. Recently, we identified the novel protein Mpo1, which is involved in PHS metabolism. However, the details of the FA α-oxidation reaction and the role of Mpo1 in PHS metabolism remained unclear. In the present study, we revealed that Mpo1 is involved in the α-oxidation of 2-hydroxy (2-OH) palmitic acid (C_16:0-COOH) in the PHS metabolic pathway. Our in vitro assay revealed that not only the Mpo1-containing membrane fraction but also the soluble fraction was required for the α-oxidation of 2-OH C_16:0-COOH. The addition of Fe²⁺ eliminated the need for the soluble fraction. Purified Mpo1 converted 2-OH C_16:0-COOH to C_15:0-COOH in the presence of Fe²⁺, indicating that Mpo1 is the enzyme body responsible for catalyzing the FA α-oxidation reaction. This reaction was also found to require an oxygen molecule. Our findings indicate that Mpo1 catalyzes the FA α-oxidation reaction as 2-OH fatty acid dioxygenase, mediated by iron(IV) peroxide. Although numerous Mpo1 homologs exist in bacteria, fungi, protozoa, and plants, their functions had not yet been clarified. However, our findings suggest that these family members function as dioxygenases.

KEYWORDS:

• dioxygenase
• fatty acid
• fatty acid α-oxidation
• phytosphingosine
• sphingolipid
• yeast

ACKNOWLEDGMENTS

We thank Yusuke Ohno for technical support and Tatsuro Naganuma, Takashi Obara, and Satoshi Ichikawa for discussion.

This work was supported by the Advanced Research and Development Programs for Medical Innovation (AMED-CREST) (grant number JP18gm0910002 to A.K.) from the Japan Agency for Medical Research and Development and KAKENHI grant numbers JP18H03976 and JP18H04664 (to A.K.) from the Japan Society for the Promotion of Science.