Enzymatic formation of manganese oxides by an Acremonium-like hyphomycete fungus, strain KR21-2.
A Mn-depositing fungus, Acremonium-like hyphomycete strain KR21-2, was isolated from a Mn deposit occurring on the wall of a storage bottle containing Mn(III, IV) oxide-coated streambed pebbles and stream water. 18S rRNA gene sequence analysis revealed that strain KR21-2 was phylogenetically related to members of the order Hypocreales within the class Ascomycetes. The spent culture medium at the stationary phase of fungal growth contained a 54-kDa protein capable of depositing Mn oxides. The enzymatic activity was inhibited by azide and o-phenanthroline. The Mn(II)-oxidizing protein possessed a laccase activity, as indicated by direct oxidation of p-phenylenediamine and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid). These results are consistent with the role assumed for laccase-like multicopper oxidase, which is proposed to be involved in the Mn(II)-oxidizing factors from some bacteria. Unlike laccases of basidiomycete fungi, however, the protein of strain KR21-2 did not produce soluble Mn(III) species in the presence of either of the Mn chelators pyrophosphate and malonate. This is the first report on the possible involvement of laccase and/or multicopper oxidase in Mn oxide deposition by ascomycetes (including their anamorphs) ubiquitous in natural environments.
Miyata
Naoyuki
N
Institute for Environmental Sciences, University of Shizuoka, Yada, Japan. miyatan@smail.u-shizuoka-ken.ac.jp
Tani
Yukinori
Y
Iwahori
Keisuke
K
Soma
Mitsuyuki
M
D000164:Acremonium / Q000145:classification*; D003470:Culture Media; D004271:DNA, Fungal / Q000032:analysis; D006999:Hypocreales / Q000145:classification / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D042845:Laccase / Q000378:metabolism*; D017895:Manganese Compounds / Q000378:metabolism*; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010087:Oxides / Q000378:metabolism*; D010802:Phylogeny; D012337:RNA, Ribosomal, 18S / Q000235:genetics; D017422:Sequence Analysis, DNA
D003470:Culture Media; D004271:DNA, Fungal; D017895:Manganese Compounds; D010087:Oxides; D012337:RNA, Ribosomal, 18S; C027424:manganese oxide; D042845:Laccase