rs1805087 in the MTR Gene: Health Conditions Explained

Last reviewed: May 12, 2026 Last updated: May 12, 2026

Written by: Jay Hastings , CEO of PlexusDx

Jay Hastings is the CEO of PlexusDx, a precision health company focused on genetic testing, blood biomarker insights, and personalized wellness recommendations. He has more than 20 years of experience across healthcare innovation, genomics, laboratory operations, healthcare investing, and strategic finance. His work has included scaling healthcare startups, leading CLIA lab integrations, and helping expand consumer access to precision health tools.

Medically reviewed by: Jayden Lee, PharmD, EMBA

Jayden Lee, PharmD, EMBA, is the PlexusDx Medical Science Liaison with a PharmD and MBA specializing in pharmacogenomics and clinical product development, with a proven ability to bridge the gap between genomic research and practical patient outcomes. Dr. Lee has more than 10 years of professional experience in clinical pharmacy, academia, and research.

This article is part of the PlexusDx Education Hub — your resource for evidence-based guidance on genetics and health. Browse all Genetics & Health education

The rs1805087 variant in the MTR gene is one of the most studied single-letter changes in human methylation biology. MTR encodes methionine synthase, an enzyme that sits at a busy metabolic crossroads, and a change at this position can subtly shift how efficiently your body recycles homocysteine. Here is what researchers have connected to rs1805087, and how to think about your own genetics without overreading a single result.

What the MTR gene does

MTR (5-methyltetrahydrofolate-homocysteine methyltransferase) builds the enzyme methionine synthase. Its job is to convert homocysteine back into methionine, using vitamin B12 as a cofactor and a methyl group donated by folate. Methionine then feeds S-adenosylmethionine (SAMe), the universal methyl donor your cells use to regulate DNA, neurotransmitters, and hundreds of other reactions.

When this reaction slows, homocysteine can accumulate and folate can become trapped in a form the body cannot easily use — sometimes called the "methyl-folate trap." MTR does not work alone: it partners with MTRR (methionine synthase reductase) to stay active, and it operates alongside the better-known MTHFR gene upstream.

The rs1805087 variant explained

rs1805087 is an A-to-G change (sometimes written A2756G) that swaps aspartate for glycine at position 919 of the protein, so you will also see it called Asp919Gly or D919G. The G allele is the minor variant, carried by a substantial minority of people worldwide. Because MTR sits at the homocysteine-to-methionine step, the functional question researchers ask is whether the variant nudges homocysteine levels up, and whether that shift interacts with B12 and folate status.

Health conditions linked to rs1805087

Association studies — not diagnoses — have connected rs1805087 to several areas of interest. Elevated plasma homocysteine is the most consistent finding, especially when B12 or folate intake is low. Because homocysteine is a cardiovascular marker, some studies have examined links to vascular health. Others have looked at neural tube defect risk in pregnancy, cognitive aging, and certain cancers, though results vary across populations and many findings are modest or mixed.

The honest summary: rs1805087 is a contributor, not a cause. It shifts probabilities within a network that also includes MTHFR C677T (rs1801133), MTRR rs1801394, diet, and lifestyle. A single variant rarely determines an outcome on its own.

How rs1805087 interacts with B12 and folate

Methionine synthase depends on vitamin B12. That dependence is why the MTR pathway is so nutrient-sensitive: the same genotype can look very different in someone with ample B12 and folate versus someone who is depleted. This is a key reason researchers study MTR variants together with nutritional status rather than in isolation, and why a genetics conversation is most useful when paired with bloodwork and a qualified provider.

What your PlexusDx genetic insights reveal

MTR sits within the methylation and one-carbon metabolism pathways that PlexusDx examines at the DNA level. The Precision Peptide Genetic Test analyzes 14 pathways, 49 peptides, 150+ genetic insights — placing variants like these in the context of the biological systems they touch, not a diagnosis or a verdict.

Seeing where you fall on variants like rs1805087, alongside MTHFR and MTRR, turns an abstract worry into a specific, informed question you can bring to your provider — the "know, don't guess" approach. Genetics is a guide, not a guarantee: your genotype is fixed, but how you support these pathways through nutrition and clinical guidance is not.

Frequently Asked Questions About rs1805087 and MTR

Is the rs1805087 G allele harmful?

No. The G allele is a common variant, not a disease. Research links it to modest shifts in homocysteine processing, particularly when B12 or folate is low. It describes a tendency within your methylation biology, not a diagnosis, and its effect depends heavily on nutrition and overall health.

Can I change how the MTR pathway functions?

You cannot change your genotype, but the MTR pathway is nutrient-responsive. Because methionine synthase needs vitamin B12 and folate, adequate intake of these nutrients supports normal function. Any supplementation decision should be made with a qualified healthcare provider using your bloodwork, not a genetic result alone.

How does MTR relate to MTHFR?

MTHFR and MTR work in sequence within one-carbon metabolism. MTHFR produces the active folate form, and MTR uses it to convert homocysteine back to methionine. Variants in both genes can influence homocysteine together, which is why they are often examined side by side rather than separately.

Want to see where your own pathways stand? Take the Precision Peptide Genetic Test to understand how your DNA shapes 14 peptide-related biological pathways — genetics as a guide, not a guarantee.

This article is part of the PlexusDx Education Hub. Browse all Genetics & Health education

The Precision Peptide Genetic Test analyzes how your genes influence peptide-related biological pathways. It does not recommend, prescribe, or determine which peptides you should use, and it does not diagnose, treat, cure, prevent, or manage any disease or condition. Consult a qualified healthcare provider before making decisions about your health.

Medical and Editorial Standards

Medical review process: This article was reviewed for medical accuracy, scientific clarity, evidence alignment, and appropriate discussion of genetics, medications, supplements, biomarkers, and health-related claims.

Sources and evidence: PlexusDx educational content is developed using peer-reviewed research, clinical literature, reputable medical references, and, where applicable, public health or regulatory guidance. References are included at the end of the article when scientific, medical, or health-related claims are discussed.

Commercial transparency: PlexusDx offers genetic testing, blood biomarker testing, personalized supplement recommendations, and related precision wellness services. Product mentions are intended to help readers understand available options and should not be interpreted as medical advice.

Important disclaimer: PlexusDx educational content is for informational purposes only and should not be used as a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making decisions about medications, supplements, genetic testing, lab testing, or health-related care.