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THE PEROXIDASE/OXIDASE ACTIVITY OF SOYBEAN LIPOXYGENASE – II. TRIPLET CARBONYLS AND RED PHOTOEMISSION DURING POLYUNSATURATED FATTY ACID AND GLUTATHIONE OXIDATION
Author(s) -
SCHULTEHERBRUGGEN THOMAS,
SIES HELMUT
Publication year - 1989
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1989.tb08444.x
Subject(s) - chemistry , photochemistry , dioxetane , lipoxygenase , polyunsaturated fatty acid , peroxidase , lipid peroxidation , singlet oxygen , linoleic acid , chemiluminescence , fatty acid , oxygen , antioxidant , biochemistry , organic chemistry , enzyme
During the aerobic reaction of soybean lipoxygenase with polyunsaturated fatty acids (linoleic, linolenic, and arachidonic acid) oxygen uptake is followed by excited carbonyl photoemission. The chemiluminescence yield of φ cl = 10 ‐10 photons/O 2 molecule consumed is enhanced 2–3 orders of magnitude by the carbonyl sensitizers 9,10‐dibromo‐anthracene‐2‐sulfonate ( k ET φ= 10 4 M ‐1 ; φ cl = 10 ‐8 photons/O 2 ) and chlorophyll‐ a ( k ET φ= 10 6 M ‐1 φ cl = 10 ‐7 photons/O 2 ), respectively. α,β‐Saturated triplet excited carbonyls as from 1,2‐dioxetane cleavage are discussed to arise from a secondary peroxidase/oxidase reaction with aldehydes formed in the course of enzymic lipid peroxidation. When 1 m M glutathione is added to the aerobic lipoxygenase/arachidonate reaction, carbonyl emission (375–455 nm) is replaced by intense red bands (630–645 nm and 695–715 nm) resembling the characteristic spectrum of ( 1 † g )O 2 ‐singlet oxygen dimol‐emission. The quantum yield (φ cl = 10 ‐8 photons/O 2 ) remains unaffected by chlorophyll indicating that the red emission is independent of excited carbonyls. The effect of GSH is attributed to dioxetane interception and subsequent glutathione peroxidation generating 1 O 2 by electron transfer from the superoxide anion radical to a peroxysulfenyl radical.