Detecting the role of Hydronium ions in the catalytic reaction of enzymes

Researchers work at the Los Alamos National Laboratory, which exploits neutrons, to first accurately assess the important role of hydronium ions in certain biological reactions. The results of this study may be helpful in the treatment of peptic ulcer disease or acid reflux disease, or allow efficient conversion of wood chips into alcoholic fuel.

Determination of elusive hydronium ions, changing roles with a proton in enzyme in an environment with a lower pH

The results of this study were published in Angewandte Chemie International Edition this week.

In previous studies, no scientist has ever directly witnessed the role of hydronium ions: a water molecule bound to an additional hydrogen ion, in high molecular catalysts. (catalytic reaction mechanisms of enzymes).

Researchers are interested in enzymes that have the potential to allow the conversion of two sugars in wood biofuels into ethanol, which is a potential fuel, because the enzyme loses its effect when the pH of the lips lower field, which is the fermentation reaction that usually occurs inside industrial yeast cells.

On the other hand, this biochemical reaction also triggered proton pump phenomenon in the stomach, creating excess acid in people suffering from stomach disease.

Hydronium ions have not been seen before researchers tried to use X-rays to understand the chemical mechanism of enzymes. This is because the small hydrogen atoms are mostly invisible under X-rays. To help realize what is visible, the researchers replaced hydrogen in their enzyme samples with deuterium, an isotope of hydrogen, with the same chemical properties as its anisotropic counterpart. Deuterium gives a clear signal when struck with neutrons. Therefore, neutrons provide a perfect method for tracking elusive hydronium ions, which appear in the pyramidal mass, in the enzyme's active site, where chemical reactions occur.

Researchers have discovered an important change in the system they are working on: in acidic environmental conditions, with a pH (below 6) hydronium ions can capture and facilitate Beneficial for the bonding of a copper-element metal ion, which is important to convert to a fermentable sugar molecule: by suddenly losing water, the H ₂ O molecule, removed by hydronium, into H ₃ O +. The space occupied by relatively large hydronium ions collapses into the tiny mass which is occupied by the remaining protons (positively charged hydrogen ion, H +). This space changes the molecular structure, preventing sugar from being attacked by enzymes.

The observed phenomenon provides an answer on why pH plays an important role in this process and makes the enzyme inactive under acidic conditions. More importantly, it asserts that hydronium ions play an important role in transporting protons in these biochemical systems.

" This is an unprecedented phenomenon, " according to Andrey Kovalevsky, a researcher, working at Los Alamos National Laboratory, USA, and the lead author of this study. " This proves: hydronium is an active chemical agent, in our studies of the enzyme's catalytic mechanism. "

This study confirms the possible roles of hydronium ions in other biological systems. In addition to acid reflux disease, the results of this study also provide a better understanding of metabolic energy transfer of living cells, in living organisms.

In addition to Andrey Kovalevsky, co-authors in this study include Suzanne Fisher, Marat Mustyakimov, Thomas Yoshida, and Paul Langan (currently working at Oak Ridge National Laboratory, USA).