Involvement of manganese peroxidase in the transformation of macromolecules from low-rank coal by Phanerochaete chrysosporium |
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Authors: | J P Ralph D E A Catcheside |
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Institution: | (1) School of Biological Sciences, Flinders University of South Australia, Bedford Park, SA 5042, Australia Tel.: +61 8 201 2335 Fax: +61 8 201 3015 e-mail: bidec@flinders.edu.au, AU |
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Abstract: | Manganese peroxidase (Mn peroxidase) catalyses the oxidation of Mn(II) to Mn(III), a diffusible non-specific oxidant likely
to be involved in the transformation of polyphenolic macromolecules from brown coal by the white-rot fungus Phanerochaete chrysosporium. We report here that solubilised macromolecules from Morwell brown coal were depolymerised by Mn(III) ions when incubated
under hyperbaric O2. However, under N2 or air they were polymerised, suggesting that net depolymerisation by Mn(III) requires molecular oxygen to inhibit coupling
of coal radicals. Coal macromolecules were also polymerised when separated by a semipermeable membrane from a culture of P. chrysosporium or from a solution of Mn peroxidase, Mn(II) and H2O2, probably by Mn(III) crossing the membrane. In oxygenated cultures in which Mn peroxidase␣was up-regulated by Mn(II), the
extent of depolymerisation correlated with cumulative Mn peroxidase activity suggesting that Mn-peroxidase-generated Mn(III)
has a central role in initial depolymerisation of coal molecules in vivo. However, mutant ME446-B17-1, which produces Mn peroxidase
but not lignin peroxidase, polymerised coal macromolecules in oxygenated cultures. In sum, it appears Mn peroxidase can both
polymerise and depolymerise brown coal macromolecules and that, in vivo, both hyperbaric O2 and lignin peroxidase are also required to force net depolymerisation to products assimilable by cells.
Received: 4 September 1997 / Received revision: 29 January 1998 / Accepted: 30 January 1998 |
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