Enzymological and structural biology investigation on the fuction of the vitamin K cycle

• Applicant: Professor Johannes Oldenburg, Ph.D.
• Subject Area: Hematology, Oncology
• Term: from 2017 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 387239457

In context of a DFG-supported research project, in 2004 we identified vitamin K epoxide reductase complex subunit 1 (VKORC1) as the central component of the vitamin K cycle (Rost 2004). Since 2012, again supported by the DFG, we were able to localize the native warfarin binding site of the VKORC1 molecule, characterize structural changes within this binding site in patients with warfarin resistance, and identify the molecular cause of deficiency of all vitamin K dependent coagulation factors in patients suffering from VKCFD2. Furthermore, we in depth characterized the enzymological properties human VKORC1. For this, the in vitro activity assay originating from the 1960s was fundamentally improved.The research project, on which we apply now, will concentrate on further characterization of VKORC1 and VKORC1L1, particularly on binding of vitamin K and warfarin and the mechanism of inhibition. Furthermore, we want to investigate the second essential enzyme of the vitamin K cycle, gamma-glutamyl-carboxylase (GGCX). This enzyme is responsible for posttranslational modification of all vitamin K dependent proteins. Mutations in this enzyme likewise lead to VKCFD. By means of a recently established HEK293 GGCX knock-out cell line we want to study function and biological relevance of GGCX. Taken together, these studies will contribute significantly to the knowledge on the vitamin K cycle and its role in different organ systems.

• DFG Programme: Research Grants
• Co-Investigator: Dr. Matthias Watzka