image: Audrey Lamb, professor and chair of the UTSA Department of Chemistry, has been awarded a $486,000 grant from the National Science Foundation to advance her team’s research on the enzymes that produce riboflavin, more commonly known as vitamin B2. view more
Credit: The University of Texas at San Antonio
Audrey Lamb, professor and chair of the UTSA Department of Chemistry, has been awarded a $486,000 grant from the National Science Foundation to advance her team’s research on the enzymes that produce riboflavin, more commonly known as vitamin B2.
The human body does not biosynthesize riboflavin yet the vitamin is essential to important biological functions such as DNA repair and cellular respiration—the means by which cells generate energy. Eating foods that contain riboflavin naturally is the only way to acquire it. Milk and eggs, for instance, contain relatively high levels of vitamin B2.
“When making a vitamin, the enzymes work in a particular order like an assembly line,” Lamb said. “Each enzyme adds or subtracts a few atoms to the compound made by the previous enzyme until the full molecule is built.”
Scientists’ current understanding of the biosynthesis of riboflavin was advanced by Adelbert Bacher and his research team at the Technical University of Munich in the 1990s. The researchers identified five enzymes that are required to form riboflavin.
Lamb’s lab, in collaboration with Graham Moran at Loyola University, Chicago, has been researching how the first three enzymes (RibA, RibB and RibD) perform the chemistry that Bacher’s team defined. Lamb and Moran’s most recent research paper was published in July in the Journal of the American Chemical Society (JACS).
Together, the researchers demonstrated that RibB only requires one magnesium ion for full catalytic activity, in contrast to a previous assumption of two. They also show that the starting molecule is not directly converted into the desired outcome molecule, but that the transition first requires the formation of at least two other compounds within the enzyme.
The five enzymes that make riboflavin work too slowly in a test tube to form enough riboflavin to be sufficient to support life. However, when the enzymes are located inside a cell, they work much faster.
Lamb hypothesizes that all five enzymes required to make riboflavin can be assembled into a molecular machine that her team has named the “riboflavinator.” This sub-microscopic machine, she said, acts inside the cell. Her research team is currently focused on how the enzymes come together to create riboflavin at a much faster rate than has been observed in a test tube.
Lamb’s latest NSF grant will fund research into the remaining two enzymes necessary for riboflavin production. Using the methodologies established in the JACS paper, the researchers will analyze how RibC and RibE perform the reactions they catalyze, and they will build the riboflavinator in a test tube to demonstrate that it is able to produce riboflavin faster than the enzymes would individually in a test environment.
“Think of it like this: you have an engine, some spark plugs, a catalytic converter, a gas tank and an axle system with wheels spread out on your driveway, just hanging out by themselves,” Lamb explained. “They can be shown doing their individual jobs. But they aren’t going to make much of a machine that can run down the highway unless you assemble them into a car.”
Lamb’s lab aims to figure out exactly how each enzyme does its job and contributes to producing riboflavin. This understanding could potentially lead to improved methods for treating diseases and improving public health.
“If we know how biologically important molecules, like vitamins, are made, we can figure out how to make medicines using similar chemical approaches or design molecules that act as drugs by stopping pathogens from doing these chemistries,” she said.