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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Unraveling the hidden catalytic activity of vertebrate class Ⅱa histone deacetylases
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Unraveling the hidden catalytic activity of vertebrate class Ⅱa histone deacetylases

机译：揭示脊椎动物Ⅱa类组蛋白脱乙酰基酶的隐藏催化活性

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Previous findings have suggested that class Ila histone deacetylases (HDACs) (HDAC4, -5, -7, and -9) are inactive on acetylated substrates, thus differing from class I and IIb enzymes. Here, we present evidence supporting this view and demonstrate that class Ma HDACs are very inefficient enzymes on standard substrates. We identified HDAC inhibitors unable to bind recombinant human HDAC4 while showing inhibition in a typical HDAC4 enzymatic assay, suggesting that the observed activity rather reflects the involvement of endogenous copurified class I HDACs. Moreover, an HDAC4 catalytic domain purified from bacteria was 1,000-fold less active than class I HDACs on standard substrates. A catalytic Tyr is conserved in all HDACs except for vertebrate class Ila enzymes where it is replaced by His. Given the high structural conservation of HDAC active sites, we predicted the class IIa His-Nε2 to be too far away to functionally substitute the class I Tyr-OH in catalysis. Consistently, a Tyr-to-His mutation in class I HDACs severely reduced their activity. More importantly, a His-976-Tyr mutation in HDAC4 produced an enzyme with a catalytic efficiency 1,000-fold higher than WT, and this "gain of function pheno type" could be extended to HDAC5 and -7. We also identified trifluoroacetyl-lysine as a class IIa-specific substrate in vitro. Hence, vertebrate class IIa HDACs may have evolved to maintain low basal activities on acetyl-lysines and to efficiently process restricted sets of specific, still undiscovered natural substrates.
机译：先前的发现表明，IIa类组蛋白脱乙酰基酶（HDACs）（HDAC4，-5，-7和-9）在乙酰化底物上没有活性，因此不同于I和IIb类酶。在这里，我们提供支持这种观点的证据，并证明Ma类HDAC在标准底物上是效率很低的酶。我们确定了HDAC抑制剂无法结合重组人HDAC4，同时在典型的HDAC4酶法测定中显示出抑制作用，这表明观察到的活性反而反映了内源性共纯化I类HDAC的参与。此外，从细菌中纯化得到的HDAC4催化域的活性比标准底物上的I类HDAC低1,000倍。催化酪氨酸在所有HDAC中均保守，除了脊椎动物类Ila酶（其被His取代）外。鉴于HDAC活性位点的高度结构保守性，我们预测IIa类His-Nε2距离太远，无法在功能上替代I类Tyr-OH。一致地，I类HDAC中的Tyr-His突变严重降低了它们的活性。更重要的是，HDAC4中的His-976-Tyr突变产生的酶的催化效率比WT高1,000倍，这种“功能表型获得”可扩展至HDAC5和-7。我们还确定了三氟乙酰赖氨酸在体外为IIa类特异性底物。因此，脊椎动物IIa类HDAC可能已经进化为在乙酰赖氨酸上维持较低的基础活性，并能有效处理有限的特定的，尚未发现的天然底物。

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