Journal article
Reversible alkaline inactivation of lignin peroxidase involves the release of both the distal and proximal site calcium ions and bishistidine co-ordination of the haem
Biochemical Journal, Vol.344(1), pp.237-244
1999
Abstract
Phanerochaete chrysosporium lignin peroxidase isoenzyme H2 (LiP H2) exhibits a transition to a stable, inactive form at pH 9.0 with concomitant spectroscopic changes. The Soret peak intensity decreases some 55% with a red shift from 408 to 412 nm; the bands at 502 nm and 638 nm disappear and the peak at 536 nm increases. The EPR spectrum changes from a signal typical of high spin ferric haem to an exclusively low spin spectrum with g = 2.92, 2.27, 1.50. These data indicate that the active pentaco-ordinated haem is converted into a hexaco-ordinated species at alkaline pH. Room temperature near-IR MCD data coupled with the EPR spectrum allow us to assign the haem co-ordination of alkali-inactivated enzyme as bishistidine. Re-acidification of the alkali-inactivated enzyme to pH 6 induces further spectroscopic changes and generates an irreversibly inactivated species. By contrast, a pH shift from 9.0 to 6.0 with simultaneous addition of 50 mM CaCl 2 results in the recovery of the initial activity together with the spectroscopic characteristics of the native ferric enzyme. Incubating with 50 mM CaCl 2 at a pH between 6.0 and 9.0 can also re-activate the enzyme. Divalent metals other than Ca 2+ do not result in restoration of activity. Experiments with 45Ca indicate that two lightly bound calcium ions per enzyme monomer are lost during inactivation and reincorporated during subsequent re-activation, consistent with the presence of two structural Ca 2+ ions in LiP H2. It is concluded that both the structural Ca 2+ ions play key roles in the reversible alkaline inactivation of LiP H2.
Details
- Title
- Reversible alkaline inactivation of lignin peroxidase involves the release of both the distal and proximal site calcium ions and bishistidine co-ordination of the haem
- Authors/Creators
- S.J. George (Author/Creator)M. Kvaratskhelia (Author/Creator)M.J. Dilworth (Author/Creator)R.N.F. Thorneley (Author/Creator)
- Publication Details
- Biochemical Journal, Vol.344(1), pp.237-244
- Publisher
- Portland Press, Ltd.
- Identifiers
- 991005543622807891
- Murdoch Affiliation
- Centre for Rhizobium Studies; School of Biological Sciences and Biotechnology
- Language
- English
- Resource Type
- Journal article
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Source: InCites
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- Citation topics
- 3 Agriculture, Environment & Ecology
- 3.87 Paper & Wood Materials Science
- 3.87.946 Ligninolytic Enzymes
- Web Of Science research areas
- Biochemistry & Molecular Biology
- ESI research areas
- Biology & Biochemistry