Catalase and glutathione, the enzymes that finish the job
Someone is selling you glutathione in a capsule, and your gut takes most of it apart before it gets anywhere. Here is the second half of your antioxidant relay, who actually runs it, and the one thing food genuinely contributes to it.
This article explains normal cell biology. It makes no claim that any food, berry or product treats, cures or prevents any condition.
The short answer
Superoxide dismutase turns the superoxide radical into oxygen and hydrogen peroxide, which is still reactive. Catalase and glutathione peroxidase are the enzymes that break the peroxide down into water. Catalase is the fast one for high concentrations, glutathione peroxidase is the precise one for everyday levels, and both are built by your own cells.
In this article
You cannot buy the enzyme, and the label knows that
Glutathione is one of the most heavily marketed words in the wellness aisle. It is sold as capsules, as sachets, as intravenous drips in clinics. What almost none of that marketing says out loud is that glutathione is a molecule your own cells build, and swallowed glutathione is largely dismantled in your gut before it can be used as anything except raw material.
That is not a reason to give up on nutrition here. It is a reason to know exactly where food does and does not enter this system, because there is a real answer, and it is more specific than the bottle suggests. It starts with what superoxide dismutase leaves behind.
Why SOD leaves a mess behind
There is a detail people skip when they talk about superoxide dismutase. SOD does not make the reactive molecule disappear. It converts one reactive molecule into another one, hydrogen peroxide, and hydrogen peroxide is the same compound sitting in a brown bottle in the bathroom cabinet. Useful in its place, and not something a cell wants accumulating.
So the antioxidant system is a relay rather than a single act. Step one converts. Step two clears. If step two did not exist, step one would be moving a problem rather than solving it.
Figure 01
The full relay, both steps
One view, no scrolling. The second row is the part this article is about.
Simplified schematic of the antioxidant enzyme pathway. GPx = glutathione peroxidase.
Catalase, the fast one
Catalase is one of the quickest enzymes known. A single catalase molecule can process an enormous number of hydrogen peroxide molecules per second, converting them into plain water and oxygen.1 You have watched it work: the foaming when hydrogen peroxide touches a cut is catalase in the tissue releasing oxygen gas.
It is concentrated in peroxisomes, small compartments inside the cell that handle a lot of chemically messy work, and it needs iron, held in a heme group, to function. Catalase shines when peroxide levels are relatively high. It is the bulk-clearance option.
Glutathione peroxidase, the precise one
Most of the time, peroxide levels are not high. They are low and constant, which is a different engineering problem, and glutathione peroxidase is the answer to it. This enzyme reduces hydrogen peroxide to water using glutathione, a small three-amino-acid molecule your cells make, as the electron donor.
The used glutathione is then recycled back into its active form by another enzyme, glutathione reductase, so the same pool keeps working. It is a loop, not a one-way consumption, which is why the body can run it continuously.
The part worth remembering: most forms of glutathione peroxidase carry a selenium atom at their active site.2 Without dietary selenium the enzyme cannot be built in its usual form. That is the cleanest example in the whole antioxidant story of food feeding a system rather than substituting for it.
Figure 02
Two enzymes, one molecule to clear
Stacked cards, not a scrolling table. They are not redundant, they cover different conditions.
Catalase Peroxisomes
- ConvertsHydrogen peroxide into water and oxygen
- CofactorIron, in a heme group
- Best atHigh peroxide concentrations, very fast
- Helper neededNone
Glutathione peroxidase Widespread
- ConvertsHydrogen peroxide into water
- CofactorSelenium at the active site
- Best atLow, everyday peroxide levels
- Helper neededGlutathione, recycled and reused
Standard human enzymology. Cofactor and localisation details as described in the cited references.
Nothing you swallow becomes one of these enzymes. What you eat becomes the parts they are built from.
What food actually contributes here
This is where marketing usually overreaches, so it is worth being exact. Catalase is a protein. Eat it and digestion takes it apart into amino acids, the same as any other protein. Swallowed glutathione is largely broken down in the gut as well. Neither one arrives in your cells as a finished working molecule because you bought a bottle of it.
What food does supply, dependably, is the input list. Selenium for glutathione peroxidase. Iron for catalase. Cysteine, an amino acid, as the limiting building block for glutathione itself. And alongside the enzymes, dietary antioxidant compounds such as vitamin C, vitamin E and flavonoids, which work in the same overall balance without being enzymes at all.
Which reverses the usual shopping logic. If the enzymes cannot be bought and the useful contribution is raw material and cofactors, then the thing worth paying for is not a bottle labelled with an enzyme name. It is food dense enough to keep supplying the inputs every day without a long ingredient list attached. Sea buckthorn belongs in that last group, as one cold-pressed fruit rather than a stack of isolated capsules.
Human Renaissance sea buckthorn puree contains 190+ naturally occurring compounds, omega 3, 6, 7 and 9, 201 mg of vitamin C per pouch, 0 g sugar and 5,640 hand-picked berries per box.
None of that is catalase or glutathione peroxidase, and this article does not suggest otherwise. It is dense whole-food nutrition that sits beside the enzyme relay, which is a smaller and more honest claim than most labels make.
Frequently asked questions
What do catalase and glutathione peroxidase do?
Both break down hydrogen peroxide. Catalase converts it into water and oxygen very quickly and works best where peroxide levels are high. Glutathione peroxidase converts it into water using glutathione as a helper molecule and handles lower, everyday levels. Together they complete the reaction that superoxide dismutase starts.
Why does the body need two different enzymes for the same molecule?
They cover different ranges and different locations. Catalase is concentrated in peroxisomes and is extremely fast at high peroxide concentrations. Glutathione peroxidase is spread more widely, including inside mitochondria, and is efficient at the low concentrations that are present most of the time.
What is glutathione?
Glutathione is a small molecule made of three amino acids, cysteine, glutamate and glycine, that your own cells build. It is the helper molecule glutathione peroxidase uses, and it is regenerated by another enzyme so it can be used again.
Can you get catalase or glutathione from food?
Not as working molecules in any straightforward way. Catalase is a protein and is digested into amino acids. Oral glutathione is broken down substantially in the gut. What food reliably supplies is the raw material and the mineral cofactors, including the amino acid cysteine and the trace mineral selenium.
Why does selenium keep coming up with glutathione peroxidase?
Most forms of glutathione peroxidase carry a selenium atom at their active site, so the enzyme cannot be built in its usual form without dietary selenium. This is the clearest example of nutrition feeding an antioxidant enzyme system rather than replacing it.
Does sea buckthorn supply these enzymes?
No, and no food does. Sea buckthorn is a whole-food source of vitamin C, flavonoids and other plant compounds that sit alongside the enzyme relay rather than inside it. The body builds the enzymes itself.
Sources
- Nandi A, Yan LJ, Jana CK, Das N. Role of Catalase in Oxidative Stress and Age-Associated Degenerative Diseases. PMC6851487
- Brigelius-Flohe R, Maiorino M. Glutathione peroxidases. PubMed 23201771
- National Center for Biotechnology Information, StatPearls. Biochemistry, Superoxide Dismutase. NBK553095
