Carbonic anhydrase is an essential enzyme found in almost all organisms; The eight types of carbonic anhydrides identified to date require a metal ion to function. But now, researchers in Japan have discovered that metal is not important for all carbonic anhydrides.
In a study published this month PMC Biology, Researchers from the Faculty of Life and Environmental Sciences at Sukuba University described two members of the COG4337 protein family, the first known examples of carbonic anhydrase enzymes that do not require the action of a metal ion.
Carbonic anhydrase promotes the conversion of carbon dioxide (CO)2) Into bicarbonate (HNO3), And vice versa. They are central to a wide range of physiological processes, including the regulation of acid-base balance, respiration and photosynthesis, and are important for all carbon-dependent organisms, from bacteria to humans. All previously identified classes of carbonic anhydrase contain zinc, cadmium, cobalt or manganese, which are essential for the activity of these enzymes, so when researchers at Sukuba University discovered that the proteins COG4337 were known to be similar to known carbonic anions, these new proteins became ions.
“Because the active site of most carbonic anhydrase is a Metal ion This facilitates the exchange between CO2 And HNO3‾ We were surprised to find that the COG4337 proteins did not require any of the eight different metals we tested, in fact they react less well in the presence of zinc, ”says lead author Professor Yoshihisa Hirakawa.
When researchers developed the COG4337 model Protein System, found to exist Active site, Or pocket, which catches CO2 When Enzyme Converts it into HNO3. Interestingly, unlike other carbonic anhydrase, these novel enzymes do not seem to reverse the HNO conversion.3CO is CO2. In addition, these COG4337 proteins were found to accumulate in the microalgae picilovillea natans’ plastids and in the mitochondria, where CO2 Metabolism takes place.
“These proteins are expressed by a number of cyanobacteria and eukaryotic microalgaes, which live in environments with very different metal contents. .
With widespread exposure to carbonic anhydrase in ecologically important microorganisms, this novel genre MetalCarbonic anhydrase, which is dependent on the global carbon cycle, may play an important role. A further understanding of how these enzymes work would be useful for artificial photosynthesis, the main source of renewable energy.
Yoshihisa Hiragawa et al., Characteristic of a new type of carbonic anhydrase that works without metal cofactors PMC Biology (2021). DOI: 10.1186 / s12915-021-01039-8
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