Let’s explore “Vitamin B9 / folate deficiency”

DHFR helps reduce folic acid and dihydrofolate to tetrahydrofolate-related forms used in cellular metabolism. This is one part of the folate system, distinct from MTHFR and folate transport into cells.

FOLH1 helps break down folate from food so it can be absorbed. This is different from the MTHFR step.

FOLR2 encodes folate receptor beta, a folate-binding protein expressed in particular cell types, including subsets of immune cells. It is distinct from the FOLR1 receptor and the SLC19A1 reduced folate carrier.

GGH encodes gamma-glutamyl hydrolase, which removes glutamate residues from folate compounds. This affects folate handling and helps explain why folate metabolism includes retention and processing as well as intake.

MTHFD1 helps move folate between forms used for different jobs in the body.

The homocysteine chapters include MTHFD1L in the wider folate-related genetic map.

Makes an enzyme involved in producing phosphatidylcholine, a component of cell membranes. Genetic findings alone do not establish a choline deficiency.

SHMT1 connects serine and glycine with folate chemistry.

VDR encodes the vitamin D receptor, which helps regulate gene activity in response to active vitamin D. A receptor variant does not by itself mean receptors are absent or that the blood vitamin D level is low.

VKORC1 encodes vitamin K epoxide reductase, part of the vitamin K recycling system used in activating clotting proteins. It is not simply a vitamin K receptor.

Encodes the reduced folate carrier, a protein involved in transporting folates into cells.

GSTO2 encodes glutathione S-transferase omega 2, a redox enzyme with dehydroascorbate reductase activity that connects glutathione chemistry with vitamin C recycling. It is a separate gene from GSTO1.