Seeing what can’t be seen
How science is opening up the black box of enzymes
Tucked in the back corner of his office, between stacks of magazines, shines the orange binding of The Complete Idiot’s Guide to Strategic Planning.
In an ironic way, surrounded by models of molecules and detailed science publications, the book fits Dr. Martin St. Maurice perfectly.
The Marquette University assistant professor of biological sciences is far from idiotic. On a daily basis he uses X-ray crystallography and diffractometers in his laboratory. Rather, it’s fitting because St. Maurice’s research discovers something simple within complexity.
Working through a grant from the National Institute of Health, St. Maurice studies the fungal enzyme urea amidolyase to see how it functions on a molecular level.
The problem: he can’t simply use a microscope.
“We could get a microscope as big as the Sears Tower and still not see these molecules,” St. Maurice explained. “They can’t be observed in visible light.”
To do so St. Maurice uses X-ray crystallography to create three-dimensional models of the molecules. The beams of the X-rays are diffracted by crystals of the molecule at certain angles and intensities, which are then measured to calculate a model of the molecule.
Suddenly, the unseeable enzyme can be represented in a wire model St. Maurice holds in his hands.
An enzyme is a molecule responsible for creating reactions within a cell. Urea amidolyase is one such enzyme found in the opportunisitic fungal pathogen, Candida albicans. In healthy persons, Candida albicans does little to no harm.
However, for those with a weakened immune system — late-stage HIV/AIDS patients, organ transplant recipients, etc. — an infection by Candida albicans can potentially be deadly. The enzyme catalyzes a reaction that allows Candida to escape from macrophages and spread throughout the body, resulting in a potentially fatal infection.
St. Maurice’s research is seeking to more fully understand the enzyme function, with the hope that the insights gained from the study might help prevent systemic Candida infections in susceptible individuals.
“The ultimate hope would be … to find these small molecule inhibitors,” St. Maurice said.
From there studies could be designed to do clinical testing of molecules that would inhibit the enzyme. For now, St. Maurice’s research is focused on understanding the basic function of the enzyme, a process that requires a great deal of patience.
Two years into the project, St. Maurice knows what the enzyme looks like, a large step from the mysterious “black box” it was before. However, the X-ray crystallography technology used to model the enzyme requires many protein crystals to be grown and frozen at certain reaction stages to be photographed.
Depending on the necessary structure and quality of the protein crystal, the growing process can take from mere days to years
St. Maurice’s project is furthering the field of biochemistry as well. Limited research has been done on enzymes with this type of structure, so the study will translate to knowledge not just about urea amidolyase, but will contribute to better describing enzyme structures as a whole.
“This is a paradigm of what is actually happening inside the cell,” St. Maurice said.
Like many of the projects done in St. Maurice’s lab, the work is both accessible and engaging for students. The grant was awarded in part because it included graduate and undergraduate work. Over the summer, seven students work in the St. Maurice’s lab.
During the school year, two students worked alongside St. Maurice on the research. In the coming months the research again will require the work of graduates and undergraduates.
Since the structure has been identified, hypotheses will soon be developed as to what parts of the enzyme are contributing to the reactions. To test these hypotheses, separate projects will be available for student initiative. St. Maurice is excited to note the opportunities and experiences this will provide students.
“It can offer a wealth of projects to train the next generation of research scientists.”
The various projects stem from the specific design of urea amidolyase. Typically enzymes have only one location for the chemistry of a reaction to take place. Urea amidolyase has four separate reaction locations, making it difficult to determine how all of the individual pieces come together to contribute to the overall reaction.
Once there is a complete description of how various componenets of urea amidolyase contribute to function , specific molecules can be tested to inhibit that function. Since urea amidolyase is present in Candida albicans but does not exist in humans, these molecules should not have any adverse effects on humans, an important factor for later clinical testing.
Generating hypotheses about how the enzyme works is the next step in the research. Studying these fundamental elements will provide important information for future health and science research.
But first, St. Maurice must simplify the complex nature of the understudied enzyme.
Research and reporting by Wyatt Massey, a junior studying writing-intensive English and advertising. Connect with him on Twitter or LinkedIn.
