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FROM THE PURSER BOOKSHELF · CHAPTER GUIDE

Genetics and the transsulfuration pathway

Follow the sulfur pathway from homocysteine toward cysteine and glutathione.

Based on teaching by Dan Purser, MD. How we prepare these guides

Educational summary

Why this matters

Follow the sulfur pathway from homocysteine toward cysteine and glutathione.

How the pieces connect

Cysteine, glutathione, oxidative stress, and energy pathways connect to this discussion. A pathway map can guide questions but cannot diagnose the effect of a gene finding.

Pathway names describe different jobs

Remethylation and transsulfuration are connected, but they are not the same process. Dr. Purser discusses MTHFR alongside CBS, MTR, MTRR and SHMT1 because these genes participate in a broader metabolic network. A finding in one gene cannot tell you the activity of the entire network. Dr. Purser also introduces homocysteinylation, redox balance and ferroptosis as mechanisms worth studying; those terms should not be read as diagnoses on a consumer genetic report.

Keep in mind

A gene list cannot diagnose you. A common variant, even in both copies, does not by itself prove high homocysteine, an immune problem, or a need for supplements.

A question for your next conversation

Does the genetic finding have a demonstrated effect on the pathway, or is the connection only proposed?

BUILD YOUR UNDERSTANDING

A few concepts, made clearer.

Cysteine

An amino acid used in protein synthesis and other metabolic processes.

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CBS

CBS is the gene symbol used for Cystathionine Beta-Synthase. This page connects its terminology with the topics in the Purser Wellness teaching encyclopedia.

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MTHFR

Makes an enzyme that helps produce a form of folate used in the processing of homocysteine. Common variants are different from rare variants that cause severe MTHFR deficiency.

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MTR

Makes the methionine synthase enzyme, which uses vitamin B12 in the conversion of homocysteine to methionine.

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