Laccases ofRigidoporus lignosus andPhellinus noxius: II. Effect ofR. lignosus laccase L1 on thioglycolic lignin of hevea

l~l~l~~~~~~~~~~~ ll ABSTRACT A laccase that has been isolated previously (1) from the Basidio- mycete, Rigidoporus lignosus, a white rot fungus of rubber tree, was used in the present study. When a thioglycolic lignin (TGL) was incu- bated in the presence of this enzyme, pronounced changes in the UV spectrum and size distribution of the substrate were observed. Sephadex gel filtration indicated that two types of reactions occurred: (1) A degradation of the polymer, as evidenced by the production of low-molecular-weight material; and (2) a condensation of some of the TGL molecules, as revealed by an increase in the fractions of higher molecular weight. Index Entries: Thioglycolic lignin TGL; Sephadex gel filtration and molecular weight variation estimation; molecular weight hetero- geneity of TGL; laccase, enzymatic lignin depolymerization and con- densation of.