TY - JOUR
T1 - Reduction of the 2,2'-azinobis(3-ethylbenzthiazoline-6-sulfonate) cation radical by physiological organic acids in the absence and presence of Manganese
AU - Collins, Patrick J.
AU - Dobson, Alan D.W.
AU - Field, Jim A.
PY - 1998/6
Y1 - 1998/6
N2 - Laccase is a copper-containing phenoloxidase, involved in lignin degradation by white rot fungi. The laccase substrate range can be extended to include nonphenolic lignin subunits in the presence of a noncatalytic cooxidant such as 2,2'-azinobis(3-ethylbenzthiazoline-6-sulfonate) (ABTS), with ABTS being oxidized to the stable cation radical, ABTS.+, which accumulates. In this report, we demonstrate that the ABTS.+ can be efficiently reduced back to ABTS by physiologically occurring organic acids such as oxalate, glyoxylate, and malonate. The reduction of the radical by oxalate results in the formation of H2O2, indicating the formation of O2.- as an intermediate. O2.- itself was shown to act as an ABTS.+ reductant. ABTS.+ reduction and H2O2 formation are strongly stimulated by the presence of Mn2+, with accumulation of Mn3n+ being observed. Additionally, 4-methyl-O-isoeugenol, an unsaturated lignin monomer model, is capable of directly reducing ABTS.+. These data suggest several mechanisms for the reduction of ABTS.+ which would permit the effective use of ABTS as a laccase cooxidant at catalytic concentrations.
AB - Laccase is a copper-containing phenoloxidase, involved in lignin degradation by white rot fungi. The laccase substrate range can be extended to include nonphenolic lignin subunits in the presence of a noncatalytic cooxidant such as 2,2'-azinobis(3-ethylbenzthiazoline-6-sulfonate) (ABTS), with ABTS being oxidized to the stable cation radical, ABTS.+, which accumulates. In this report, we demonstrate that the ABTS.+ can be efficiently reduced back to ABTS by physiologically occurring organic acids such as oxalate, glyoxylate, and malonate. The reduction of the radical by oxalate results in the formation of H2O2, indicating the formation of O2.- as an intermediate. O2.- itself was shown to act as an ABTS.+ reductant. ABTS.+ reduction and H2O2 formation are strongly stimulated by the presence of Mn2+, with accumulation of Mn3n+ being observed. Additionally, 4-methyl-O-isoeugenol, an unsaturated lignin monomer model, is capable of directly reducing ABTS.+. These data suggest several mechanisms for the reduction of ABTS.+ which would permit the effective use of ABTS as a laccase cooxidant at catalytic concentrations.
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U2 - 10.1128/aem.64.6.2026-2031.1998
DO - 10.1128/aem.64.6.2026-2031.1998
M3 - Article
AN - SCOPUS:0031799214
SN - 0099-2240
VL - 64
SP - 2026
EP - 2031
JO - Applied and environmental microbiology
JF - Applied and environmental microbiology
IS - 6
ER -