Taha Tarek A, El-Alwani Mazen, Hannun Yusuf A, Obeid Lina M
Division of General Internal Medicine, Ralph H. Johnson Veterans Administration Hospital, Charleston, SC 29401, USA.
FEBS Lett. 2006 Nov 13;580(26):6047-54. doi: 10.1016/j.febslet.2006.09.070. Epub 2006 Oct 12.
Previous work has identified sphingosine kinase-1 (SK1) as a substrate for the cysteine protease cathepsin B in vitro. In this study, the mechanism of SK1 cleavage by cathepsin B was investigated. We identified two initial cleavage sites for the protease, the first at histidine 122 and the second at arginine 199. Mutation analysis showed that replacement of histidine 122 with a tyrosine maintained the activity of SK1 while significantly reducing cleavage by cathepsin B at the initial cleavage site. The efficacy of cleavage of SK1 at arginine 199, however, was not affected. These studies demonstrate that SK1 is cleaved by cathepsin B in a sequential manner after basic amino acids, and that the initial cleavages at the two identified sites occur independently of each other.
先前的研究已确定鞘氨醇激酶-1（SK1）在体外是半胱氨酸蛋白酶组织蛋白酶B的底物。在本研究中，对组织蛋白酶B切割SK1的机制进行了研究。我们确定了该蛋白酶的两个初始切割位点，第一个位于组氨酸122处，第二个位于精氨酸199处。突变分析表明，用酪氨酸取代组氨酸122可维持SK1的活性，同时显著减少组织蛋白酶B在初始切割位点的切割。然而，组织蛋白酶B对精氨酸199处SK1的切割效率不受影响。这些研究表明，SK1在碱性氨基酸之后被组织蛋白酶B依次切割，并且在两个已确定位点的初始切割相互独立发生。
