Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Scientists convert modern enzyme into its hypothesized ancestor

31.10.2006
By making a single substitution in the amino acid sequence of a modern enzyme, scientists have changed its function into that of a theoretical distant ancestor, providing the first experimental evidence for the common origin of the two distinct enzyme types.

The research, conducted by a team that includes scientists from the U.S. Department of Energy's Brookhaven National Laboratory and the Karolinska Institute in Stockholm, Sweden, will be published online the week of October 30, 2006, by the Proceedings of the National Academy of Sciences.

"It's as if we turned back the clock nearly 2.5 billion years, to the time when oxygen first appeared in Earth's atmosphere, to get a snapshot of how enzymes evolved to deal with reactive oxygen species," said Brookhaven biochemist John Shanklin, lead author on the paper.

Oxygen, while essential for many life processes, can also exist in potentially toxic forms, such as superoxide and hydroxyl radicals, as well as hydrogen peroxide. After the first photosynthetic organisms appeared on Earth some 2.5 billion years ago, pumping oxygen into the atmosphere, organisms with enzymes capable of deactivating these reactive oxygen species had an increased chance of survival.

... more about:
»Oxidase »acid »amino »amino acid »ancestor »desaturase

Scientists have theorized that the first oxygen-detoxifying enzymes were simple oxidases, which combine reactive forms of oxygen, such as peroxide, with hydrogen ions (protons) and electrons to yield water (H2O). While these enzymes have little in common with more modern biosynthetic enzymes that mediate oxygen chemistry, they share certain structural and sequence characteristics around their active sites -- namely, a pair of iron atoms for binding oxygen within a similar four-helix bundle. These similarities suggested the possibility of a common origin, but experimental evidence was lacking -- until now.

The Brookhaven/Karolinska team had previously performed a structural comparison of the active site of a modern desaturase enzyme (which uses activated oxygen to remove two hydrogens from fatty acids) with that of a simple peroxidase. They used a stand-in for oxygen binding in the active site (because oxygen itself does not stay bound long enough for studies) and produced molecular-level crystal structures using high intensity beams of x-rays at the National Synchrotron Light Source at Brookhaven Lab and the MAX Lab at the University of Lund Synchrotron in Sweden.

These crystal structures revealed remarkable similarities, with the single major difference being a change in one amino acid residue adjacent to the oxygen-binding site: The oxidase had an acidic residue capable of donating protons to the oxygen to form water while the desaturase did not.

Based on this difference, the scientists hypothesized that if they engineered a "desaturase" with an acidic amino acid residue in place of the non-reactive one, they would convert the desaturase to an oxidase. Using the tools of molecular biology, this is exactly what they did.

"Substituting aspartic acid at this site on the desaturase made a huge change," Shanklin said.

The new enzyme's desaturase activity decreased 2000-fold while its oxidase activity increased 31-fold compared with the original desaturase. New crystal structures, derived at the European Synchrotron Radiation Facility in France, revealed that the substitution placed the acid group into the ideal position for donating protons to the oxygen.

"Usually, when enzymes evolve from a common ancestor, there are many amino acids that change to change the function," Shanklin said. "So it is remarkable that changing the identity of a single amino acid in an enzyme of 400 amino acids can make such a dramatic switch in the chemical reaction it performs. This finding, that such a simple change can dramatically alter function, provides experimental support for the hypothesis that these two enzyme groups share a common origin."

Karen McNulty Walsh | EurekAlert!
Further information:
http://www.bnl.gov

Further reports about: Oxidase acid amino amino acid ancestor desaturase

More articles from Life Sciences:

nachricht Molecular Force Sensors
20.09.2017 | Max-Planck-Institut für Biochemie

nachricht Foster tadpoles trigger parental instinct in poison frogs
20.09.2017 | Veterinärmedizinische Universität Wien

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

Im Focus: Quantum Sensors Decipher Magnetic Ordering in a New Semiconducting Material

For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.

Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...

Im Focus: Fast, convenient & standardized: New lab innovation for automated tissue engineering & drug

MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems Holding GmbH about commercial use of a multi-well tissue plate for automated and reliable tissue engineering & drug testing.

MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems...

Im Focus: Silencing bacteria

HZI researchers pave the way for new agents that render hospital pathogens mute

Pathogenic bacteria are becoming resistant to common antibiotics to an ever increasing degree. One of the most difficult germs is Pseudomonas aeruginosa, a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Molecular Force Sensors

20.09.2017 | Life Sciences

Producing electricity during flight

20.09.2017 | Power and Electrical Engineering

Tiny lasers from a gallery of whispers

20.09.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>