Secondary metabolites are assembled by enzymes that often perform reactions with high selectivity and specificity. Many of these enzymes also tolerate variations in substrate structure, exhibiting promiscuity that enables various applications of a given biocatalyst. However, initial enzyme characterization studies frequently do not explore beyond the native substrates. This limited assessment of substrate scope contributes to the difficulty of identifying appropriate enzymes for specific synthetic applications. Here, we report the natural function of cyanobacterial SxtG, an amidinotransferase involved in the biosynthesis of paralytic shellfish toxins, and demonstrate its ability to modify a breadth of non-native substrates. In addition, we report the first X-ray crystal structure of SxtG, which provides rationale for this enzyme's substrate scope. Taken together, these data confirm the function of SxtG and exemplify its potential utility in biocatalytic synthesis.

中文翻译：

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麻痹性贝类毒素Amidinotransferase的底物混杂。

次生代谢物是由通常以高选择性和特异性进行反应的酶组装而成。这些酶中的许多酶还耐受底物结构的变化，表现出混杂性，使得能够对给定的生物催化剂进行各种应用。但是，最初的酶表征研究通常不会探索超出天然底物的范围。对底物范围的这种有限的评估导致难以识别用于特定合成应用的合适的酶。在这里，我们报告了蓝细菌SxtG的自然功能，这是一种参与麻痹性贝类毒素生物合成的酰胺基转移酶，并证明了其修饰多种非天然底物的能力。此外，我们报告了SxtG的第一个X射线晶体结构，为这种酶提供了理论依据。底物范围。综上所述，这些数据证实了SxtG的功能，并证明了其在生物催化合成中的潜在效用。