Vanillyl alcohol oxidase (VAO) is a fungal flavoenzyme that converts a wide range of para-substituted phenols. The products of these conversions, e.g. vanillin, coniferyl alcohol and chiral aryl alcohols, are of interest for several industries. VAO is the only known fungal member of the 4-phenol oxidising (4PO) subgroup of the VAO/PCMH flavoprotein family. While the enzyme has been biochemically characterised in great detail, little is known about its physiological role and distribution in fungi. We have identified and analysed novel, fungal candidate VAOs and found them to be mostly present in Pezizomycotina and Agaricomycotina. The VAOs group into three clades, of which two clades do not have any characterised member. Interestingly, bacterial relatives of VAO do not form a single outgroup, but rather split up into two separate clades. We have analysed the distribution of candidate VAOs in fungi, as well as their genomic environment. VAOs are present in low frequency in species of varying degrees of relatedness and in regions of low synteny. These findings suggest that fungal VAOs may have originated from bacterial ancestors, obtained by fungi through horizontal gene transfer. Because the overall conservation of fungal VAOs varies between 60 and 30% sequence identity, we argue for a more reliable functional prediction using critical amino acid residues. We have defined a sequence motif P-x-x-x-x-S-x-G-[RK]-N-x-G-Y-G-[GS] that specifically recognizes 4PO enzymes of the VAO/PCMH family, as well as additional motifs that can help to further narrow down putative functions. We also provide an overview of fingerprint residues that are specific to VAOs.

中文翻译：

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香草醇氧化酶的起源。

香兰醇氧化酶（VAO）是一种真菌黄素酶，可转化多种对位取代的酚。这些转化的产物，例如香兰素，松柏油基醇和手性芳基醇，在一些行业中是令人感兴趣的。VAO是VAO / PCMH黄素蛋白家族的4-酚氧化（4PO）子组中唯一已知的真菌成员。尽管已对生化酶进行了详细的生化表征，但对其生理作用和在真菌中的分布知之甚少。我们已经鉴定并分析了新颖的真菌候选VAO，发现它们主要存在于Pezizomycotina和Agaricomycotina中。VAO分为三个进化枝，其中两个进化枝没有任何特征成员。有趣的是，VAO的细菌亲属没有形成一个单一的外群，而是分成了两个独立的进化枝。我们已经分析了候选VAO在真菌中的分布及其基因组环境。VAO在不同程度的相关性物种和低同化区域中的出现频率较低。这些发现表明，真菌VAO可能起源于细菌的祖先，真菌是通过水平基因转移由真菌获得的。由于真菌VAO的总体保守性在60％到30％的序列同一性之间变化，我们主张使用关键氨基酸残基进行更可靠的功能预测。我们定义了一个序列基序PxxxxSxG- [RK] -NxGYG- [GS]，它可以特异性识别VAO / PCMH家族的4PO酶，以及可以帮助进一步缩小推定功能的其他基序。我们还概述了VAO特有的指纹残留。