LACCASE COMPONENT OF THE CERIPORIOPSIS-SUBVEMISPORA LIGNIN-DEGRADING SYSTEM

Laccase activity in the lignin-degrading fungus Ceriporiopsis subvermi spora was associated with several proteins in the broth of cultures gr own in a defined medium, Activity,vas not increased significantly by a dding 2,5-xylidine or supplemental copper to the medium, Higher activi ty, associated with two major isoenzymes, developed in cultures grown on a wheat bran medium. These two isoenzymes were purified to homogene ity. L1 and L2 had isoelectric points of 3.4 and 4.8, molecular masses of 71 and 68 kDa, and approximate carbohydrate contents of 15 and 10% , respectively, Data indicated 4 copper atoms per mel. L1 and L2 had o verlapping pH optima in the range of 3 to 5, depending on the substrat e, and exhibited half-lives of 120 acid 50 min at 60 degrees C., They were strongly inhibited by sodium azide and thioglycolic acid but not by hydroxylamine or EDTA, The isoenzymes oxidized 1,2,4,5-tetramethoxy benzene but not other methoxybenzene congeners, A variety of usual lac case substrates, including lignin-related phenols and ABTS [2,2'-azino -bis(3-ethylbenzthiazoline-6-sulfonic acid)], were also oxidized, Kine tic parameters were similar to those of the laccases of Coriolus versi color. The N-terminal amino acid sequence (20 residues for L1) showed significant homology to those of laccases of other white rot basidiomy cetes but not to those of the laccases of Agaricus bisporus or Neurosp ora crassa.