Identification and Characterization of a Putative Dihydroorotase, KPN01074, from Klebsiella pneumoniae
作者:Chuan-Cheng Wang、Huai-Wen Tsau、Wei-Ti Chen、Cheng-Yang Huang
DOI:10.1007/s10930-010-9272-2
日期:2010.8
Dihydroorotase (DHO; EC 3.5.2.3) is an essential metalloenzyme in the biosynthesis of pyrimidine nucleotides. Here, we identified and characterized DHO from the pathogenic bacterium Klebsiella pneumoniae (Kp). The activity of KpDHO toward l-dihydroorotate was observed with K m = 0.04 mM and V max = 8.87 μmol/(mg min). Supplementing the standard growth medium with Co2+, Mn2+, Mg2+, or Ni2+ increased enzyme activity. The catalytic activity of KpDHO was inhibited with Co2+, Zn2+, Mn2+, Cd2+, Ni2+, and phosphate ions. Substituting the putative metal binding residues His17, His19, Lys103, His140, His178, and Asp251 with Ala completely abolished KpDHO activity. However, the activity of the mutant D251E was fourfold higher than that of the wild-type protein. On the basis of these biochemical and mutational analyses, KpDHO (KPN01074) was identified as type II DHO.
二氢乳清酸酶(DHO;EC 3.5.2.3)是嘧啶核苷酸生物合成中一种必不可少的金属酶。在此,我们鉴定并描述了肺炎克雷伯氏菌(Kp)中的DHO。KpDHO对l-二氢乳清酸的活性为K m=0.04mM,V max=8.87μmol/(mg·min)。在标准培养基中添加Co2+、Mn2+、Mg2+或Ni2+可提高酶活性。Co2+、Zn2+、Mn2+、Cd2+、Ni2+和磷酸根离子可抑制KpDHO的催化活性。用Ala取代推测的金属结合残基His17、His19、Lys103、His140、His178和Asp251,可完全消除KpDHO的活性。然而,突变体D251E的活性比野生型蛋白高四倍。根据这些生化分析和突变分析,KpDHO(KPN01074)被鉴定为II型DHO。