MOLECULAR ENZYMOLOGY
Dr Tim Mantle
Tim Mantle, BSc, PhD
Phone: + 353-1-896-1612
Fax: + 353 - 1 - 6772400
Email: tmantle@tcd.ie
Location: Room 6.22, Biomedical Sciences Institute |
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Research Interests
Research in the Molecular Enzymology Group centres on structural, kinetic and regulatory aspects of a number of enzymes.
The main project areas are:
Biliverdin-IXa reductase as a pharmacological target for neonatal jaundice.
This is an SFI funded project and involves structural and kinetic studies on BVR-A and BVR-B coupled with novel approaches to develop biliverdin reductase inhibitors (BVRIs). Successful inhibition of BVR-A is predicted to result in transient hyperbiliverdinaemia and we are constructing knock out mice to determine whether there is any toxicity associated with elevated biliverdin-IXa levels.
Structural and kinetic studies on GST-P1-1.
Glutathione S-transferase P1-1 (GST-P1-1) is the only representative of the Pi-class of GST (the other major classes, Alpha, Mu and Theta have not been subject to evolutionary constraint and have undergone significant gene duplication). This form is expressed at very low levels in normal rat hepatocytes, however in preneoplastic cells it is a major polypeptide. In mouse hepatocytes this enzyme is under androgenic control so that male mice express very high levels. There is considerable interest that overexpression of GST-P1-1 may promote carcinogenesis as male mice are far more prone to liver cancer than females. Kinetic studies have defined a regulatory site on the enzyme and in conjunction with chemical modification studies should permit a mechanistic framework to complement recent three-dimensional structure determinations conducted in collaboration with Dr M. Coll (Barcelona). We now have "snapshots" of the "free" enzyme, the enzyme-glutathione complex and the enzyme-glutathione-adduct complex. It seems clear that the thiolate anion of GSH is stabilised by a group of water molecules. We are trying to determine the basis for some subtle differences between the human and the mouse enzyme, and in particular the pK of cysteine-47 (which may function as a sensor for the GSH/GSSG ratio) which is 7.3 for the mouse and is reported to be 4.2 for the human enzyme. We have analysed "silicon mutants" and these studies suggest that the nature of the residue at position-56 modulates the availability of lysine-54 to interact with the thiolate of cysteine-47. Mutagenesis studies have confirmed this hypothesis.
The transient kinetics of sulphatase A
Sulphatase A is an excellent model for studying unstable steady-states and various contrived oscillatory phenomena. Current work involves developing novel theoretical and experimental approaches with this system.
Research Personnel
Research Students:
Heberto Rios Trevino
Mechanism of interaction of glutathione S-transferase P1-1 (GSTP1) with jun N-terminal kinase (JNK): Implications for aberrant regulation of apoptosis
Recent Publications by the Molecular Enzymology Group
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