GPX1, rs1050450, and how your body turns selenium into antioxidant defense
One small DNA swap sets how briskly your antioxidant enzyme answers when selenium shows up.
GPX1 is the gene for glutathione peroxidase 1, an enzyme that mops up hydrogen peroxide and other reactive byproducts before they chew up your cells. The catch: it's useless without selenium sitting in its active center. No selenium, no working enzyme. The variant on this page, rs1050450, swaps a single amino acid (proline for leucine) in the protein, and that swap seems to change how readily the enzyme cranks up its activity as selenium becomes available. So the real question isn't whether you have the gene. It's how efficiently your version of it uses the selenium you eat. One heads-up before you check your data: most research writes this variant as C and T, while a 23andMe or AncestryDNA export usually prints it as G and A. Same variant, opposite strand. We use the G/A version below because that's what your raw file shows.
What GPX1 does
Builds glutathione peroxidase 1, an antioxidant enzyme that neutralizes hydrogen peroxide and lipid peroxides inside your cells.
Runs entirely on selenium. The enzyme carries a selenium atom (as selenocysteine) at its working core, so its activity rises and falls with your selenium status.
The rs1050450 variant changes one amino acid, proline to leucine, in the protein. Studies tie the leucine version to a weaker activity response when selenium goes up.
It's a dial, not a switch. Every genotype still makes a functional enzyme. The open question is how steeply activity climbs as selenium becomes available.
Your variants, decoded
The proline-to-leucine swap in glutathione peroxidase 1. In your raw export the alleles read as G and A. The research literature writes the same spot as C (proline, the common, more responsive form) and T (leucine, the variant). Your 23andMe or AncestryDNA file may print the complementary letters, so don't be thrown if you see C/T instead of G/A.
| GG | Two copies of the common (proline) form. In the study below, GPx1 activity tracked selenium most tightly in this group: the enzyme ramps up well when selenium is around. Standard selenium needs apply. |
| GA | One common copy, one variant (leucine) copy. An in-between response: the enzyme still answers to selenium, just less briskly than GG. Most people carry at least one copy of each. |
| AA | Two copies of the variant (leucine) form. In the study, this group showed the weakest, non-significant link between selenium and enzyme activity, which points to a blunted response. Not a deficiency, not a diagnosis. Just a flatter return on the same selenium. |
We show genotypes on the forward strand and ignore letter order. Your own export may print the complementary letters. Same result either way.
What the research suggests
GPx1 can't work without selenium in its active site. In the study below, the enzyme's activity climbed with plasma selenium most strongly in people with the common proline (GG) form and most weakly in those with two variant leucine (AA) copies. A variant carrier who's also running low on selenium has the least margin, so the practical step is making sure selenium intake is adequate. Adequate, not maximal: selenium's safe window is narrow, so confirm you're actually low before supplementing instead of stacking it on top of a decent diet.
PubMed 19415410 · in 405 adults, GPx1 enzyme activity correlated with plasma selenium most strongly in proline/proline carriers (r=0.44) and least in leucine/leucine carriers (r=0.25, not significant), showing the variant allele blunts how the enzyme responds to selenium.
Educational only, not medical advice. “General evidence” means the finding is real, but the benefit isn’t specific to your genotype.
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Questions
What does GPX1 actually do?
It builds glutathione peroxidase 1, an enzyme that breaks down hydrogen peroxide and oxidized fats inside your cells before they pile up and do oxidative damage. It's one of your front-line antioxidant enzymes. It only works when selenium is bolted into its active site.
Why does selenium keep coming up?
Because the enzyme literally can't function without it. Selenium sits at the catalytic core as selenocysteine. When selenium is scarce, GPx1 activity drops no matter which rs1050450 genotype you carry. When it's plentiful, your genotype shapes how fully the enzyme takes advantage of it.
I have the AA genotype. Is that bad?
No. AA means two copies of the leucine version, which research links to a flatter enzyme response as selenium goes up. It's a quirk of efficiency, not a deficiency or a disease. Plenty of people are AA and perfectly healthy. Take it as a reason to make sure you're getting enough selenium, not a reason to worry.
My export shows C and T, but this page uses G and A. Did I read it wrong?
You read it fine. GPX1 sits on the minus strand of the chromosome, so the variant gets written two ways. Researchers use C (proline) and T (leucine) from the coding strand. Consumer raw files usually report G and A from the forward strand. C matches G, T matches A. Same variant, just mirrored.
Does this mean I should take a selenium supplement?
Not automatically. This page tells you how your enzyme tends to respond to selenium, not whether you're low on it. Selenium has a narrow safe range and too much causes real problems, so know your intake first (Brazil nuts, seafood, and eggs are rich sources) before adding pills. Considering a supplement? Talk it through with a doctor or dietitian first.