Division of Bioorganic Chemistry, Faculty of Chemistry, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50-370, Wrocław, Poland.
Amino Acids. 2014 May;46(5):1313-20. doi: 10.1007/s00726-014-1694-2. Epub 2014 Feb 27.
Leukotriene A4 hydrolase (LTA4H--EC 3.3.2.6) is a bifunctional zinc metalloenzyme, which processes LTA4 through an epoxide hydrolase activity and is also able to trim one amino acid at a time from N-terminal peptidic substrates via its aminopeptidase activity. In this report, we have utilized a library of 130 individual proteinogenic and unnatural amino acid fluorogenic substrates to determine the aminopeptidase specificity of this enzyme. We have found that the best proteinogenic amino acid recognized by LTA4H is arginine. However, we have also observed several unnatural amino acids, which were significantly better in terms of cleavage rate (k cat/K m values). Among them, the benzyl ester of aspartic acid exhibited a k cat/K m value that was more than two orders of magnitude higher (1.75 × 10(5) M(-1) s(-1)) as compared to L-Arg (1.5 × 10(3) M(-1) s(-1)). This information can be used for design of potent inhibitors of this enzyme, but may also suggest yet undiscovered functions or specificities of LTA4H.
白三烯 A4 水解酶（LTA4H-EC 3.3.2.6）是一种双功能锌金属酶，通过环氧化物水解酶活性处理 LTA4，并且还能够通过其氨肽酶活性一次从 N 末端肽基底物中修剪一个氨基酸。在本报告中，我们利用了 130 种个体蛋白和非天然氨基酸荧光底物文库来确定该酶的氨肽酶特异性。我们发现，LTA4H 识别的最佳蛋白氨基酸是精氨酸。然而，我们还观察到几种非天然氨基酸，它们在切割速度（k cat/K m 值）方面明显更好。其中，天冬氨酸的苄酯表现出的 k cat/K m 值比 L-Arg（1.5×10³ M⁻¹ s⁻¹）高两个数量级以上（1.75×10⁵ M⁻¹ s⁻¹）。这些信息可用于设计该酶的有效抑制剂，但也可能表明 LTA4H 具有尚未发现的功能或特异性。
