Affiliation:
1. Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, United Kingdom
Abstract
ABSTRACT
Actinomycetes secrete into their surroundings a suite of enzymes involved in the biodegradation of plant lignocellulose; these have been reported to include both hydrolytic and oxidative enzymes, including peroxidases. Reports of secreted peroxidases have been based upon observations of peroxidase-like activity associated with fractions that exhibit optical spectra reminiscent of heme peroxidases, such as the lignin peroxidases of wood-rotting fungi. Here we show that the appearance of the secreted pseudoperoxidase of the thermophilic actinomycete
Thermomonospora fusca
BD25 is also associated with the appearance of a heme-like spectrum. The species responsible for this spectrum is a metalloporphyrin; however, we show that this metalloporphyrin is not heme but zinc coproporphyrin. The same porphyrin was found in the growth medium of the actinomycete
Streptomyces viridosporus
T7A. We therefore propose that earlier reports of heme peroxidases secreted by actinomycetes were due to the incorrect assignment of optical spectra to heme groups rather than to non-iron-containing porphyrins and that lignin-degrading heme peroxidases are not secreted by actinomycetes. The porphyrin, an excretory product, is degraded during peroxidase assays. The low levels of secreted peroxidase activity are associated with a nonheme protein fraction previously shown to contain copper. We suggest that the role of the secreted copper-containing protein may be to bind and detoxify metals that can cause inhibition of heme biosynthesis and thus stimulate porphyrin excretion.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Reference36 articles.
1. Antonini
E.
Brunori
M.
Hemoglobin and myoglobin in their reactions with ligands.
1971
North-Holland Publishing Co.
Amsterdam The Netherlands
2. Saccharification of straw by actinomycete enzymes.;Ball A. S.;J. Gen. Microbiol.,1988
3. Characterization of a novel non-heme-containing extracellular peroxidase from Thermomonospora fusca.;Ball A. S.;Biochem. Soc. Trans.,1995
4. The role of actinomycetes in plant litter decomposition.;Ball A. S.;Recent Res. Dev. Soil Biol. Biochem.,1997
5. Characterization of a coproporphyrin-protein complex from Rhodobacter capsulatus.;Biel A. J.;FEMS Microbiol. Lett.,1991
Cited by
48 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献