Department of Medical Biochemistry and Microbiology, Uppsala University, BMC, Box 582, 751 23 Uppsala, Sweden.
Biochem Biophys Res Commun. 2012 Aug 3;424(3):503-7. doi: 10.1016/j.bbrc.2012.06.144. Epub 2012 Jul 4.
Tripeptidyl-peptidase II (TPP II) is a giant cytosolic peptidase with a proposed role in cellular protein degradation and protection against apoptosis. Beside its well-characterised exopeptidase activity, TPP II also has an endopeptidase activity. Little is known about this activity, and since it could be important for the physiological role of TPP II, we have investigated it in more detail. Two peptides, Nef(69-87) and LL37, were incubated with wild-type murine TPP II and variants thereof as well as TPP II from human and Drosophila melanogaster. Two intrinsically disordered proteins were also included in the study. We conclude that the endopeptidase activity is more promiscuous than previously reported. It is also clear that TPP II can attack longer disordered peptides up to 75 amino acid residues. Using a novel FRET substrate, the catalytic efficiency of the endopeptidase activity could be determined to be 5 orders of magnitude lower than for the exopeptidase activity.
三肽基肽酶 II（TPP II）是一种巨大的胞质内肽酶，据推测在细胞蛋白降解和防止细胞凋亡中发挥作用。除了其特征明显的外肽酶活性外，TPP II 还具有内肽酶活性。目前对这种活性知之甚少，由于它可能对 TPP II 的生理作用很重要，因此我们对此进行了更详细的研究。两种肽，Nef(69-87)和 LL37，与野生型鼠 TPP II 及其变体以及来自人和果蝇的 TPP II 孵育。本研究还包括两种固有无序蛋白质。我们的结论是，内肽酶活性比以前报道的更具混杂性。显然，TPP II 可以攻击长达 75 个氨基酸残基的更长的无序肽。使用一种新颖的 FRET 底物，可以确定内肽酶活性的催化效率比外肽酶活性低 5 个数量级。
