The researchers mainly focus on the enzyme P450 StaP, which belongs to the cytochrome P450 enzyme family. These enzymes are involved in metabolic and biosynthetic reactions, including the activation and degradation of drugs in humans, and the synthesis of medically relevant natural products.
P450 StaP’s active site consists of a sulfur-bound iron atom enclosed in a large hydrocarbon ring called heme. It catalyzes the oxidation of a five-ring compound called chromopyrrolic acid (CPA) and facilitates the formation of an intramolecular carbon–carbon bond to generate a six-ring staurosporine precursor. This carbon–carbon bond formation is unusual for P450 enzymes, which typically insert an oxygen atom into bonds. The researchers demonstrated that water molecules mediate this carbon–carbon coupling.
Nagano and co-workers had previously revealed that strong interactions held CPA tightly in a binding pocket, modulating proton and electron transfer reactions between substrate and enzyme. However, they observed that those interactions kept the substrate away from the heme oxygen, impeding any direct contact, and thus proton transfer, between the two species.
In their latest work, they mutated the enzyme by replacing a residue positioned between the two water molecules with hydrocarbons, which significantly decreased its activity. They also substituted CPA with a chlorine-containing compound (CCA) and discovered that the chlorine atom prevented water molecules from approaching the heme. Further, they observed decreased activity in presence of CCA, highlighting the importance of water in the mechanism.
“CCA is very poor substrate but we had no idea why this happens,” says Nagano. Since his collaborator proposed that this water molecule was very likely to be a key player in this enzyme catalysis, they ran a detailed computational investigation. They found that two water molecules in the enzyme active site acted as a proton relay between CPA and the heme.
“Similar water-assisted proton transfer between heme and substrate is also found in horseradish peroxidase (HRP), another heme enzyme,” explains Nagano. “The natural substrate-bound HRP has a water molecule close to the substrate and heme as we have observed in CPA-bound P450 StaP.” The researchers’ ultimate goal is to transpose this carbon–carbon coupling to other P450 enzymes and generate new staurosporine-like therapeutic agents.
1. Wang, Y., Chen, H., Makino, M., Shiro, Y., Nagano, S., Asamizu, S., Onaka, H. & Shaik, S. Theoretical and experimental studies of the conversion of chromopyrrolic acid to an antitumor derivative by cytochrome P450 StaP: the catalytic role of water molecules. Journal of the American Chemical Society 131, 6748–6762 (2009).
The corresponding author for this highlight is based at the RIKEN Photon Science Research Division, Biometal Science Laboratory
Decoding the genome's cryptic language
27.02.2017 | University of California - San Diego
New risk factors for anxiety disorders
24.02.2017 | Julius-Maximilians-Universität Würzburg
On January 15, 2009, Chesley B. Sullenberger was celebrated world-wide: after the two engines had failed due to bird strike, he and his flight crew succeeded after a glide flight with an Airbus A320 in ditching on the Hudson River. All 155 people on board were saved.
On January 15, 2009, Chesley B. Sullenberger was celebrated world-wide: after the two engines had failed due to bird strike, he and his flight crew succeeded...
In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport
Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...
The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.
The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...
Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...
13.02.2017 | Event News
10.02.2017 | Event News
09.02.2017 | Event News
27.02.2017 | Materials Sciences
27.02.2017 | Interdisciplinary Research
27.02.2017 | Life Sciences