Bourbonnais R, Paice M G
Pulp and Paper Research Institute of Canada, Pointe Claire, Quebec.
Biochem J. 1988 Oct 15;255(2):445-50. doi: 10.1042/bj2550445.
The basidiomycete Pleurotus sajor-caju mineralizes ring-14C-labelled lignin (dehydrogenative polymer) when grown in mycological broth. Under these conditions, two veratryl alcohol oxidase (VAO) enzymes were found in the culture medium. They oxidized a number of aromatic alcohols to aldehydes and reduced O2 to H2O2. The enzymes were purified by ion-exchange and gel-permeation chromatography. The final step of purification on Mono Q resolved the activity into two peaks (VAO I and VAO II). Both enzymes had the same Mr, approx. 71,000, but their isoelectric points differed slightly, 3.8 for VAO I and 4.0 for VAO II. Their amino acid compositions were similar except for aspartic acid/asparagine and glycine. Both enzymes are glycoproteins and contain flavin prosthetic groups. Their pH optima were around 5, and kinetic constants and specificities were similar. 4-Methoxybenzyl alcohol was oxidized the most rapidly, followed by veratryl alcohol. Not all aromatic alcohols were oxidized, neither were non-aromatic alcohols. Cinnamyl alcohol was oxidized at the gamma position. The VAO enzymes thus represent a significantly different route for veratryl alcohol oxidation from that catalysed by the previously found lignin peroxidases from Phanerochaete chrysosporium. The role of the oxidases in biodegradation might be to produce H2O2 during oxidation of lignin fragments.
担子菌侧耳在真菌培养液中生长时，能使带有14C标记的木质素（脱氢聚合物）矿化。在这些条件下，在培养基中发现了两种藜芦醇氧化酶（VAO）。它们将多种芳香醇氧化为醛，并将O2还原为H2O2。这些酶通过离子交换和凝胶渗透色谱法进行纯化。在Mono Q上的最后一步纯化将活性分离为两个峰（VAO I和VAO II）。两种酶的相对分子质量相同，约为71,000，但它们的等电点略有不同，VAO I为3.8，VAO II为4.0。除天冬氨酸/天冬酰胺和甘氨酸外，它们的氨基酸组成相似。两种酶都是糖蛋白，含有黄素辅基。它们的最适pH约为5，动力学常数和特异性相似。4-甲氧基苄醇氧化最快，其次是藜芦醇。并非所有芳香醇都能被氧化，非芳香醇也不能被氧化。肉桂醇在γ位被氧化。因此，VAO酶代表了一条与之前发现的黄孢原毛平革菌的木质素过氧化物酶催化的藜芦醇氧化途径显著不同的途径。氧化酶在生物降解中的作用可能是在木质素片段氧化过程中产生H2O2。
