CHARACTERIZATION OF A NOVEL MANGANESE PEROXIDASE-LIGNIN PEROXIDASE HYBRID ISOZYME PRODUCED BY BJERKANDERA SPECIES STRAIN BOS55 IN THE ABSENCE OF MANGANESE

A novel manganese-dependent peroxidase (MnP) isozyme produced in manga nese-free cultures of Bjerkandera sp. strain BOS55 was purified and ch aracterized, The production of the enzyme was greatly stimulated by th e exogenous addition of various physiological organic acids such as gl ycolate, glyoxylate, and oxalate, The physical properties of the enzym e are similar to those of MnP isozymes from different white rot fungi (M-r = 43,000, pi 3.88, and epsilon(407) (nm) = 123 mM(-1) cm(-1)). Th e Bjerkandera MnP was efficient ire the oxidation of Mn(II), as indica ted by the kinetic constants (low K-m of 51 mu m and turnover number o f 59 s(-1)). Furthermore, the isozyme was able to oxidize various subs trates in the absence of manganese, such as 2,6-dimethoxyphenol, guaia col, ABTS, 3-hydroxyanthranilic acid, and o- and p-anisidine. An inter esting characteristic of the isozyme was its ability to oxidize nonphe nolic substrates, veratryl alcohol and 1,4-dimethoxybenzene, without m anganese addition. The affinity for veratryl alcohol (K-m = 116 mu M) and its turnover number (2.8 s(-1)) are comparable tee those of lignin peroxidase (LiP) isozymes from other white rot fungi, Manganese at co ncentrations greater than 0.1 mM severely inhibited the oxidation of v eratryl alcohol. The results suggest that this single isozyme is a hyb rid between MnP and LiP found in other white rot fungi. The N-terminal amino acid sequence showed a very high homology to those of both MnP and LiP isozymes from Trametes versicolor.