Protein acetylation is a highly frequent protein modification. However, comparatively little is known about its enzymatic machinery. N‐α‐acetylation (NTA ) and ε‐lysine acetylation (KA ) are known to be catalyzed by distinct families of enzymes (NAT s and KAT s, respectively), although the possibility that the same GCN 5‐related N‐acetyltransferase (GNAT ) can perform both functions has been debated. Here, we discovered a new family of plastid‐localized GNAT s, which possess a dual specificity. All characterized GNAT family members display a number of unique features. Quantitative mass spectrometry analyses revealed that these enzymes exhibit both distinct KA and relaxed NTA specificities. Furthermore, inactivation of GNAT 2 leads to significant NTA or KA decreases of several plastid proteins, while proteins of other compartments were unaffected. The data indicate that these enzymes have specific protein targets and likely display partly redundant selectivity, increasing the robustness of the acetylation process in vivo . In summary, this study revealed a new layer of complexity in the machinery controlling this prevalent modification and suggests that other eukaryotic GNAT s may also possess these previously underappreciated broader enzymatic activities.

中文翻译：

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双赖氨酸和 N 末端乙酰转移酶揭示了蛋白质乙酰化的复杂性。

蛋白质乙酰化是一种非常频繁的蛋白质修饰。然而，人们对其酶促机制知之甚少。N-α-乙酰化 (NTA) 和 ε-赖氨酸乙酰化 (KA) 已知由不同的酶家族（分别为 NAT 和 KAT）催化，尽管相同的 GCN 5 相关 N-乙酰转移酶（ GNAT ）是否可以执行这两种功能一直存在争议。在这里，我们发现了一个新的质体定位 GNAT 家族，它具有双重特异性。所有 GNAT 家族成员都表现出许多独特的特征。定量质谱分析表明，这些酶表现出独特的 KA 和宽松的 NTA 特异性。此外，GNAT 2 失活导致几种质体蛋白的 NTA 或 KA 显着降低，而其他区室的蛋白不受影响。数据表明这些酶具有特定的蛋白质靶标，并且可能表现出部分冗余的选择性，从而增加了体内乙酰化过程的稳健性。总之，这项研究揭示了控制这种普遍修饰的机制的新一层复杂性，并表明其他真核 GNAT 也可能拥有这些以前未被充分认识的更广泛的酶活性。