Dc. Goodwin et al., THE ROLE OF OXALATE IN LIGNIN PEROXIDASE-CATALYZED REDUCTION - PROTECTION FROM COMPOUND-III ACCUMULATION, Archives of biochemistry and biophysics, 315(2), 1994, pp. 267-272
Reduction may be an important step in the degradation of some highly o
xidized environmental pollutants by Phanerochaete chrysosporium. Ligni
n peroxidases (LiP) from P. chrysosporium are able to catalyze reducti
ve reactions using veratryl alcohol (VA) as a mediator and either oxal
ate or EDTA as electron donors. Reduction of oxygen to superoxide, mon
itored by oxygen consumption, was used as a measure of the reductive a
ctivity of LiP. In the presence of EDTA, the rate of O-2 reduction cat
alyzed by LiP decreased with time and increasing concentrations of H2O
2. When oxalate replaced EDTA, LiP-catalyzed O-2 reduction did not dec
rease with time, and increasing concentrations of H2O2 increased the d
uration and extent of O-2 reduction. LiP was converted to the compound
III state in the presence of EDTA, H2O2, and veratryl alcohol. When o
xalate replaced EDTA, compound II was observed. The importance of the
veratryl alcohol cation radical (VA(+)) in the conversion of LiP compo
und III to active enzyme has been previously examined (D. P. Barr and
S. D. Aust, 1994, Arch. Biochem. Biophys. 311, 378-382). We propose th
at rapid reduction of VA(+) by EDTA results in accumulation of LiP com
pound III and the loss of activity resulting in a decrease in LiP-cata
lyzed reduction reactions. Oxalate is less effective in reducing the V
A(+), therefore, some VA(+) remains to convert compound III to active
enzyme and maintain LiP-catalyzed reduction reactions. Thus oxalate, a
normal secondary metabolite of P. chrysosporium, is a suitable candid
ate for mediating reduction reactions by LiP in vivo. (C) 1994 Academi
c Press, Inc.