Elizabeth Gillam

The molecular evolution of cytochrome P450 Enzymes: biological catalysts of unprecedented versatility.

Cytochrome P450 enzymes (CYPs, P450s) especially those responsible for drug metabolism in humans, are the unifying theme of the research in our lab. These fascinating enzymes are catalysts of exceptional versatility, and functional diversity. In humans they are principally responsible for the clearance of a practically unlimited variety of chemicals from the body, but are also critical in many important physiological processes. In other organisms (plants, animals, bacteria, fungi, almost everything!) they carry out an unprecedented range of functions, such as defense, chemical communication, neural development and even pigmentation. P450s are involved in the biosynthesis of an unequalled range of potent, biologically active natural products in microbes, plants and animals, including many antibiotics, plant and animal hormones, signalling molecules, toxins, flavours and fragrances. We are studying how P450s have evolved to deal with novel substrates by reconstructing ancestral precursors and evolutionary pathways, to answer such questions as how did the koala evolve to live on eucalyptus leaves, a toxic diet for most mammals.

The capabilities of P450s are only just coming to be fully recognized and structural studies on P450s should yield critical insights into how enzyme structure determines function. For example, recently we discovered that P450s are present within cells in the Fe(II) form, a finding that has led to a radical revision of the dogma concerning the P450 catalytic cycle, and has implications for the control of uncoupling of P450 activity in cells. Importantly, the biotechnological potential of P450s remains yet to be exploited. All of the specific research themes detailed below take advantage of our recognized expertise in the expression of recombinant human cytochrome P450 enzymes in bacteria. Our group is interested in finding out how P450s work and how they can be made to work better.

Artificial evolution of P450s for drug development and bioremediation: a way of exploring the sequence space and catalytic potential of P450s. The demonstrated catalytic diversity of P450 enzymes makes them the ideal starting material for engineering sophisticated chemical reagents to catalyse difficult chemical transformations. We are using artificial (or directed) evolution to engineer enzymes that are more efficient, robust and specialized than naturally occurring enzymes with the aim of selecting for properties that are commercially useful in the areas of drug discovery and development and bioremediation of pollutants in the environment. The approach we are using also allows us to explore the essential sequence and structural features that underpin all ~12000 known P450s so as to determine how they work.

Synthetic biology of enzymes for clean, green, solar-powered chemistry in drug development, bioremediation and biosensors. We have identified ancestral enzymes that are extremely thermostable compared to their modern counterparts, making them potentially very useful in industry, since they can withstand long incubations at elevated temperatures. They can be used as ‘off the shelf’ reagents to catalyse useful chemistry, such as in in drug discovery and development, fine chemicals synthesis, and cleaning up the environment. Working with drug companies, we are exploring how they can be best deployed in chemical processes and what structural features make them efficient, robust and specialized. We are also immobilizing P450s in virus-like-particles as ‘designer’ reagents that can be recovered from reactions and reused. To make such processes cheaper and more sustainable, we are using photosynthesis to power P450 reactions for clean, green biocatalysis in microalgae.

Biosketch:

After graduating from UQ with first class Honours in Biochemistry, Elizabeth took up a Royal Commission for the Exhibition of 1851 Overseas Scholarship to pursue doctoral work at Oxford University then undertook postdoctoral work at the Center in Molecular Toxicology and Department of Biochemistry at Vanderbilt University School of Medicine with Prof. F.P. Guengerich. She returned to UQ in 1993 to take up a position in Pharmacology and joined the School of Chemistry and Molecular Biosciences in 2009 as a Professor of Biochemistry.