Date of Award
Summer 8-23-2015
Degree Type
Thesis
Degree Name
Master of Science (MS)
Department
Chemistry
First Advisor
Lihua Jin, PhD
Second Advisor
Caitlin Karver, PhD
Third Advisor
Kyle Grice, PhD
Abstract
Histone deacetylases (HDAC) and matrix metalloproteinases (MMPs) are metalloenzymes with catalytic Zn2+ ions that are over-expressed in a number of physiological conditions; thus, inhibiting these enzymes is an important therapeutic approach for many diseases. An HDAC structural mimetic was developed using a ligand, bis(2-picolyl)amine (BPA), that strongly chelated Zn2+ and did not dissociate upon addition of an HDAC inhibitor. Using Isothermal Titration Calorimetry (ITC) it was found that BPA binds Zn2+ very strongly in a 1:1 stoichiometric ratio. Two known zinc- binding HDAC inhibitors, acetohydroxamic acid and 8-hydroxyquinoline, were used to study the HDAC inhibitor interaction with the BPA-Zn2+ complex using ITC. Results confirmed that the BPA did not dissociate from Zn2+ upon titration of either of the inhibitors and that the BPA- Zn2+ complex left adequate coordination sites on Zn2+ such that a BPA-Zn2+-Inhibitor complex was formed. The interactions of three members of the tetracycline family antibiotics with Zn2+ and Ca2+ were also studied using ITC and/or UV- Vis spectroscopy. Though widely known for their antimicrobial properties, the tetracyclines have been reported to inhibit MMPs by binding structural Ca2+ and Zn2+ ions. Chemically modified tetracyclines have been developed that lack the antimicrobial activity but still inhibit MMPs to prevent further antibacterial resistance development. ITC studies of the interaction of Zn2+ with tetracycline, minocycline, and tigecycline were performed at pH 6.80 and at pH 7.50. Of the three antibiotics, minocycline was found to have the highest affinity for Zn2+, two- and four-times as high as for tigecycline and tetracycline, respectively. The composition of the tetracycline complex with Zn2+ was pH-dependent while that of minocycline and tigecycline with Zn2+ were not. Previous work in the Jin lab investigated the interaction of tetracycline, minocycline, and tigecycline with Ca2+ at pH 6.80 and at pH 7.50 using ITC. The stoichiometries for the interactions of tetracycline, minocycline and tigecycline with Zn2+ and Ca2+ obtained using ITC were confirmed using UV-Vis spectroscopy analyzed with Job’s method. Knowledge about active site metal-ion contribution to HDAC inhibitor binding energetics and about the energetics of tetracycline binding to structural MMP metal ions will enhance the design of HDAC and MMP inhibitors.
Recommended Citation
Robinson, Sophia, "TOWARD IMPROVING METALLOENZYME INHIBITOR DESIGN: A THERMODYNAMIC STUDY OF SMALL MOLECULE INTERACTIONS WITH ZINC(II) AND CALCIUM(II)" (2015). College of Science and Health Theses and Dissertations. 113.
https://via.library.depaul.edu/csh_etd/113
SLP Collection
no