Division of Applied Microbiology, Department of Chemistry, Lund University, SE-22100 Lund, Sweden.
BMC Biotechnol. 2014 Apr 9;14:25. doi: 10.1186/1472-6750-14-25.
The conversion of vanillin to vanillylamine is a key step in the biosynthetic route towards capsaicinoids in pungent cultivars of Capsicum sp. The reaction has previously been annotated to be catalysed by PAMT (putative aminotransferase; [GenBank: AAC78480.1, Swiss-Prot: O82521]), however, the enzyme has previously not been biochemically characterised in vitro.
The biochemical activity of the transaminase was confirmed by direct measurement of the reaction with purified recombinant enzyme. The enzyme accepted pyruvate, and oxaloacetate but not 2-oxoglutarate as co-substrate, which is in accordance with other characterised transaminases from the plant kingdom. The enzyme was also able to convert (S)-1-phenylethylamine into acetophenone with high stereo-selectivity. Additionally, it was shown to be active at a broad pH range.
We suggest PAMT to be renamed to VAMT (vanillin aminotransferase, abbreviation used in this study) as formation of vanillin from vanillylamine could be demonstrated. Furthermore, due to high stereoselectivity and activity at physiological pH, VAMT is a suitable candidate for biocatalytic transamination in a recombinant whole-cell system.
香草醛向香草基胺的转化是辣椒素生物合成途径中在辛辣品种中的关键步骤。该反应以前被注释为由 PAMT（假定的氨基转移酶；[GenBank：AAC78480.1，Swiss-Prot：O82521]）催化，然而，该酶以前尚未在体外进行生物化学表征。
通过直接测量纯化重组酶的反应，证实了转氨基酶的生化活性。该酶接受丙酮酸和草酰乙酸作为辅酶，但不接受 2-氧代戊二酸，这与来自植物界的其他已表征的氨基转移酶一致。该酶还能够以高立体选择性将（S）-1-苯乙胺转化为苯乙酮。此外，还表明该酶在较宽的 pH 范围内具有活性。
我们建议将 PAMT 更名为 VAMT（香草醛氨基转移酶，本研究中使用的缩写），因为可以证明香草基胺形成香草醛。此外，由于高立体选择性和生理 pH 值下的活性，VAMT 是重组全细胞系统中生物催化转氨基的合适候选物。
