Enzyme-bound pentadienyl and peroxyl radicals in purple lipoxygenase

Journal Article · Tue Jul 24 04:00:00 EDT 1990 · Biochemistry; (USA)

DOI:https://doi.org/10.1021/bi00481a020· OSTI ID:5988439

Nelson, M J; Seitz, S P; Cowling, R A ^[1]

---

1. E. I. du Pont de Nemours Company, Wilmington, DE (USA)

Samples of purple lipoxygenase prepared by addition of either 13-hydroperoxy-9,11-octadecadienoic acid or linoleic acid and oxygen to ferric lipoxygenase contain pentadienyl and/or peroxyl radicals. The radicals are identified by the g values and hyperfine splitting parameters of natural abundance and isotopically enriched samples. The line shapes of their EPR spectra suggest the radicals are conformationally constrained when compared to spectra of the same radicals generated in frozen linoleic acid. Further, the EPR spectra are unusually difficult to saturate. All of this implies that these species are bound to the enzyme, possibly in proximity to the iron. Addition of natural abundance hydroperoxide under {sup 17}O-enriched O{sub 2} leads to the {sup 17}O-enriched peroxyl radical, while the opposite labeling results in the natural abundance peroxyl radical, demonstrating the exchange of oxygen. Both radicals are detected in samples of purple lipoxygenase prepared with either linoleic acid or hydroperoxide under air. Addition of the hydroperoxide in the absence of oxygen favors the pentadienyl radical. The authors propose that addition of either linoleic acid or hydroperoxide to ferric lipoxygenase leads to multiple mechanistically connected enzyme complexes, including those with (hydro)peroxide, peroxide, peroxyl radical, pentadienyl radical, and linoleic acid bound. This hypothesis is essentially identical with the proposed radical mechanism of oxygenation of polyunsaturated fatty acids by lipoxygenase.

• OSTI ID: 5988439
• Journal Information: Biochemistry; (USA), Journal Name: Biochemistry; (USA) Vol. 29:29; ISSN 0006-2960; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ALKYL RADICALS
BIOCHEMISTRY
CARBOXYLIC ACIDS
CHEMISTRY
DECANOIC ACID
DEUTERIUM COMPOUNDS
ELECTRON SPIN RESONANCE
ENZYMES
HYDROGEN COMPOUNDS
HYPERFINE STRUCTURE
LINOLEIC ACID
MAGNETIC RESONANCE
MONOCARBOXYLIC ACIDS
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXIDOREDUCTASES
OXYGENASES
PENTYL RADICALS
PEROXY RADICALS
RADICALS
RESONANCE