BMC Seminar: Wednesday, 1st February at 12:00, Room 343, Læknagarður
Speaker: Jens Guðmundur Hjörleifsson , PhD student. Faculty of Physical Sciences, Chemistry Division, University of Iceland.
Title: Study of a highly efficient bacterial alkaline phosphatase: Dimer dynamics and ionic influences on activity and stability
Abstract: Understanding structure-function relationships in enzymes is fundamental for novel enzymatic application in industry and research as well as to understand the role of enzymes in disease. Alkaline phosphatase (AP) is a well known homodimeric metallo enzyme and widespread in nature. It hydrolyses or transphosphorylates phosphate-ester containing substrates and has broad substrate specificity. In bacteria, its main role is believed to be to supply the bacteria with inorganic phosphate for metabolism. In vertebrates, some proposed roles are in bone formation, bicarbonate secretion, lipid absorption and even defense against gut bacteria. The AP in this study is from a marine bacterium, Vibrio splendidus (VAP), and has been shown to be cold-active and unstable, even on ice. It’s extreme thermo-intolerance has not yet been linked to any molecular event such as, dimer dissocation or metal ion depletion. The main focus of the study is to seek an answer the question why the enzyme is only active as a dimer and how cold adaptation influences dimerization and dynamics of the dimer. Recently we have found that both the activity and stability is greatly affected in ionic strength close to ocean salinity (stable at 40°C in 500 mM NaCl). This ionic activation and stabilization is highly dependant on pH in the pH range 8-10. This observation has helped us understand the nature of the rate limiting step in the enzymes reaction scheme and how it switches in the pH range 8-10. Finally, preliminary results for studying dimer dissociation, using a small fluorescent probe, will be presented.