Heme d has been isolated from the purified terminal oxidase complex of Escherichia coli strain MR43L/F152. After conversion to the metal-free methyl ester form, termed chlorin d, its structure was investigated. It was determined to be a chlorin, that is, a porphyrin with one pyrrole ring saturated so that the βcarbons have sp3 hybridization. Substituents were identified by means of visible, infrared, mass spectrometric, and 1H NMR spectroscopy. The configuration of substituents was assigned by means of nuclear Overhauser enhancements between nearest neighbors and by the differential effects of a lanthanide shift reagent. The proposed structure of chlorin d contains the substituents 1-methyl, 2-vinyl, 3-methyl, 4-vinyl, 5-methyl, 5-hydroxyl, 6-(γ-lactone), 7-propionyl methyl ester, and 8-methyl. Ring C is the saturated pyrrole, and the 6-substitutent is an unusual spiro-γ-lactone.
ASJC Scopus subject areas
- Colloid and Surface Chemistry