Bell pepper fruit fatty acid hydroperoxide lyase is a cytochrome P450 (CYP74B)

Abstract

Fatty acid hydroperoxide lyases cleave a C−C bond adjacent to a hydroperoxide group in lipoxygenase derived lipid hydroperoxides to form short-chain aldehydes and oxo-acids. Previously, we showed that fatty acid hydroperoxide lyase from bell pepper fruits is a heme protein whose spectrophotometric properties greatly resemble a cytochrome P450. In order to ascertain the relationship of it to the P450 gene family, we have cloned cDNA encoding fatty acid hydroperoxide lyase from immature bell pepper fruits. The cDNA encodes 480 amino acids, and shares homology with P450s mostly at the C terminus. The heme binding cysteine is recognizable at position 441. The most closely related P450 is allene oxide synthase (CYP74A), with which it has 40% identity. It qualifies the lyase as a member of a new P450 subfamily, CYP74B. From this finding, the enzyme is thought to be a novel member of P450 specialized for the metabolism of lipid peroxides.