Tyrosinases, peat and ticking bombs
Wetlands are found on every continent: from Indonesian mangrove forests, Congolese river delta landscapes, and Siberian permafrost bogs to Austrian salt marshes. As long as they are wet or damp, these habitats are powerful allies in times of climate crisis. Their best-known representatives, the peatlands, cover between four and five percent of the global land area. Since the last ice age they have stored more CO₂ than they have released, because they interrupt an important cycle.
“There is currently as much carbon stored in peatlands as there is CO₂ in the entire atmosphere,” explains chemist Felix Panis. This scientist at the University of Vienna is investigating the complex chemical processes that take place in many wetlands. His research objective is to understand how greenhouse gas emissions from peatlands, mangrove forests, and similar ecosystems change in times of global warming – and, ultimately, how these emissions can be influenced.
The disrupted cycle
Plants absorb CO₂ from the air. From the carbon, they produce complex molecules such as sugar, and from that, in turn, carbohydrates, which they use to build their biomass – including roots, leaves, or stems. When a birch tree dies in the forest, fungi and bacteria enter the scene, producing and releasing enzymes that break down the dead biomass of the birch tree. This process releases carbon back into the air as CO₂, and the carbon cycle is complete.
“Peatlands are different. They preserve everything,” says Felix Panis. “The underlying reason is the so-called phenols that are found in the water.” Phenols are chemical compounds that are produced by plants as part of their metabolism – for example, to fend off bacteria or as an unintentional byproduct. Bog plants such as sphagnum mosses and bog birches also produce phenols. “One can see them,” says Panis. Pools in Siberian bogs are dark brown or black: the color of the phenolic compounds. The fact that bogs and other wetlands contain phenols and are wet on top makes them effective carbon sinks.
This is because phenols can inhibit the enzymes that break down dead plant matter. As a result, these enzymes remain inactive or are active to a very limited extent, and the carbon that makes up sphagnum mosses or bog birches does not enter the atmosphere.
Felix Panis is studying how climate change affects enzyme activity in the world’s largest peatlands. He has demonstrated that certain enzymes could accelerate the breakdown of carbon stores. In 2024, the chemist received the Zero Emissions Award for his research project.
Just a bit of air?
But phenols aren’t indestructible. Specialized bacteria produce enzymes that can break them down. One such type of enzymes is known as tyrosinases. “You could say they’re the villains of this story,” says Felix Panis, going on to explain: “Because tyrosinase enzymes need oxygen to break down phenols.” In wetlands like bogs, where the soil is permanently damp or wet, they don’t come into contact with it, but that could change as a result of global warming – with significant negative consequences.
Felix Panis is now the first to demonstrate the role tyrosinase enzymes play in bogs and how global warming affects them. Taking a multi-step approach, Panis first investigated whether the bacteria that produce tyrosinases are present in bogs and, if so, whether they are active. Finally, he studied how higher temperatures and increased oxygen levels affect the tyrosinases and their activity.
Lots of data, a stroke of luck
It all began with a water sample from a salt marsh at Lake Neusiedl. Felix Panis and his colleagues used so-called primers to amplify around 20 DNA fragments from this sample – in other words the “blueprint” for the tyrosinases contained within.
The researchers compared these DNA fragments with sequenced DNA data from an online database – and managed to match one of them to a complete DNA sequence in the database. “That was a real stroke of luck,” Panis says today. This match made it possible to get E. coli bacteria to produce the enzyme and then extract it. At the end of the process, the researchers obtained a tyrosinase sample that they were able to use for further investigations.
The team then went back to the computer, where they screened additional databases for DNA sequences of tyrosinases – and they found what they were looking for. “Over 100 samples in which tyrosinase enzymes were found came from wetlands,” notes Felix Panis. Most of them included information about the specific collection site of the sample. This enabled the researchers to prove that tyrosinases occur in wetlands across many climate zones: from lowland bogs in Germany to mangrove forests in Indonesia.
The role of tyrosinases
“In a next step we had to determine whether the tyrosinase enzymes we had found also acted on the phenols found in bogs,” Panis recounts. They took a closer look at the preparation they had produced in the lab. The salt marsh from which the original sample originated is relatively basic, with a pH value of nine. Experiments showed that the tyrosinase enzymes are active at precisely this pH value. Finally, the researchers combined phenols found globally and also in the salt marsh with five expressed tyrosinases. This told them that the enzyme breaks down most of the phenols.
By means of this complex process, Felix Panis and his colleagues were able to demonstrate for the first time what role tyrosinases play in wetlands. Their findings help assess how flows of greenhouse gas emerging from peatlands are evolving in times of climate crisis – and how we might intervene.
Can these carbon bombs be defused?
According to Felix Panis, wetlands are carbon time bombs. If the climate crisis continues to escalate, they could ignite. With conditions becoming increasingly dry and hot, bogs can dry out as a consequence. This enables oxygen to penetrate these formerly wet soils, and tyrosinases begin to break down phenols. In the absence of phenols, other enzymes can break down plant residues composed of carbon. Thus, climate change leads to the release of massive amounts of CO₂ into the atmosphere, thereby intensifying global warming. This vicious cycle is already underway and could become exacerbated.
The researchers are currently conducting laboratory experiments to determine whether these developments are occurring and, if so, to what extent. “We want to know what really happens when it gets drier and warmer,” explains Panis. In addition, they are experimenting with an attempt at a solution involving so-called methoxylated phenols.
In order to understand this, one must zoom in to the molecular level. Many phenols consist of a benzene ring to which OH – i.e. an oxygen molecule and a hydrogen molecule – is attached. “However, there are also phenols with a methyl group – such as CH3 – in place of the hydrogen molecule,” explains Panis. These methoxylated phenols cannot be broken down by tyrosinase enzymes. As a result, they can continue to be effective in inhibiting the enzymes that decompose dead plant parts. Currently, the researchers are investigating what happens when methoxylated phenols are introduced, and the initial results are promising. “It looks like there’s light at the end of the tunnel,” says Panis.
Climate protection remains the best approach
The Vienna research team has now demonstrated for the first time that influencing tyrosinases also affects how much CO₂ escapes from wetlands. This finding can serve as a basis for potential future outdoor research with tyrosinases and methoxylated phenols. But, as Panis notes, this is not going to happen anytime soon.
Until then, it is important to pursue a remedial approach that takes effect immediately and with certainty: reducing greenhouse gas emissions into the atmosphere. The less the atmosphere warms, the longer it will take for wetlands to dry out and come into contact with oxygen. Effective climate protection helps keep carbon stored in bogs and similar habitats for even longer. It’s actually quite simple, says Panis: “Wetlands must remain wet.”
About the researcher
Felix Panis earned his Ph.D. in chemistry from the University of Vienna. At the Department of Biophysical Chemistry, he conducts research on tyrosinases, specialized enzymes that play a central role in the carbon cycle of wetlands. In 2024, he was awarded the “Zero Emissions Award” by the alpha+ Foundation of the Austrian Science Fund (FWF) for the project “Wetland tyrosinases: global contributors to climate change” (2023–2028).
Selected Publications
Bacterial tyrosinases as extracellular sources of quinone-based electron shuttles in soil, in: Soil Biology and Biochemistry 2025
Biochemical Investigations of Five Recombinantly Expressed Tyrosinases Reveal Two Novel Mechanisms Impacting Carbon Storage in Wetland Ecosystems, in: Environmental Science & Technology 2023
The Novel Role of Tyrosinase Enzymes in the Storage of Globally Significant Amounts of Carbon in Wetland Ecosystems, in: Environmental Science & Technology 2022
