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首页> 外文期刊>Journal of bacteriology >Peptidase E, a Peptidase Specific for N-Terminal Aspartic Dipeptides, Is a Serine Hydrolase
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Peptidase E, a Peptidase Specific for N-Terminal Aspartic Dipeptides, Is a Serine Hydrolase

机译：肽酶E是N末端天冬氨酸二肽特异的肽酶，是一种丝氨酸水解酶。

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Salmonella enterica serovar Typhimurium peptidase E (PepE) is an N-terminal Asp-specific dipeptidase. PepE is not inhibited by any of the classical peptidase inhibitors, and its amino acid sequence does not place it in any of the known peptidase structural classes. A comparison of the amino acid sequence of PepE with a number of related sequences has allowed us to define the amino acid residues that are strongly conserved in this family. To ensure the validity of this comparison, we have expressed one of the most distantly related relatives (Xenopus) in Escherichia coli and have shown that it is indeed an Asp-specific dipeptidase with properties very similar to those of serovar Typhimurium PepE. The sequence comparison suggests that PepE is a serine hydrolase. We have used site-directed mutagenesis to change all of the conserved Ser, His, and Asp residues and have found that Ser120, His157, and Asp135 are all required for activity. Conversion of Ser120 to Cys leads to severely reduced (104-fold) but still detectable activity, and this activity but not that of the parent is inhibited by thiol reagents; these results confirm that this residue is likely to be the catalytic nucleophile. These results suggest that PepE is the prototype of a new family of serine peptidases. The phylogenetic distribution of the family is unusual, since representatives are found in eubacteria, an insect (Drosophila), and a vertebrate (Xenopus) but not in the Archaea or in any of the other eukaryotes for which genome sequences are available.
机译：肠沙门氏菌血清型鼠伤寒肽酶E（PepE）是一种N末端Asp特异性二肽酶。 PepE不受任何经典的肽酶抑制剂的抑制，并且其氨基酸序列也未将其置于任何已知的肽酶结构类别中。 PepE氨基酸序列与许多相关序列的比较使我们能够定义在该家族中高度保守的氨基酸残基。为了确保该比较的有效性，我们表达了大肠杆菌中最亲近的亲戚（ Xenopus ），并证明它确实是Asp特异性的二肽酶。其性质与鼠伤寒血清型PepE非常相似。序列比较表明PepE是丝氨酸水解酶。我们已经使用定点诱变来改变所有保守的Ser，His和Asp残基，并且发现Ser120，His157和Asp135都是活性所必需的。 Ser120向Cys的转化导致严重降低（10 4 -倍）活性，但仍可检测到，硫醇试剂可抑制该活性，但不能抑制母体的活性。这些结果证实该残基很可能是催化亲核试剂。这些结果表明PepE是丝氨酸肽酶新家族的原型。该家族的系统发育分布是不寻常的，因为在真细菌，昆虫（果蝇）和脊椎动物（非洲爪蟾）中发现了代表，但在 Archaea中却没有发现或任何其他可获得基因组序列的真核生物。

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