Characterization of the enzymatic activity of human kallikrein 6: Autoactivation, substrate specificity, and regulation by inhibitors.
Human kallikrein 6 (hK6) is a trypsin-like serine protease, member of the human kallikrein gene family. Studies suggested a potential involvement of hK6 in the development and progression of Alzheimer's disease. The serum levels of hK6 might be used as a biomarker for ovarian cancer. To gain insights into the physiological role of this enzyme, we sought to determine its substrate specificity and its interactions with various inhibitors. We produced the proform of hK6 and showed that this enzyme was able to autoactivate, as well as proteolyse itself, leading to inactivation. Kinetic studies indicated that hK6 cleaved with much higher efficiency after Arg than Lys and with a preference for Ser or Pro in the P2 position. The efficient degradation of fibrinogen and collagen types I and IV by hK6 indicated that this kallikrein might play a role in tissue remodeling and/or tumor invasion and metastasis. We also demonstrated proteolysis of amyloid precursor protein by hK6 and determined the cleavage sites at the N-terminal end of the protein. Inhibition of hK6 was achieved via binding to different serpins, among which antithrombin III was the most efficient.
Magklara
Angeliki
A
Department of Pathology and Laboratory Medicine, Mount Sinai Hospital, 600 University Avenue, Toronto, Ont., Canada M5G 1X5.
Mellati
Ali A
AA
Wasney
Gregory A
GA
Little
Sheila P
SP
Sotiropoulou
Georgia
G
Becker
Gerald W
GW
Diamandis
Eleftherios P
EP
D000595:Amino Acid Sequence; D016564:Amyloid beta-Protein Precursor / Q000737:chemistry / Q000378:metabolism; D004789:Enzyme Activation; D006801:Humans; D007610:Kallikreins / Q000378:metabolism*; D007700:Kinetics; D008969:Molecular Sequence Data; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology; D013379:Substrate Specificity
D016564:Amyloid beta-Protein Precursor; D015842:Serine Proteinase Inhibitors; C103551:KLK6 protein, human; D007610:Kallikreins