Other forms present may include pteroylglutamic acid (PGA), 5-formyltetrahydrofolic acid (5-formylTHF), tetrahydrofolic acid
(THF), and other reduced forms (10, 11), and possibly 4-[alpha]-hydroxy-5-methylTHF (hmTHF) (12).
Trimethoprim is an analog of a portion of another substrate in the pathway, dihydrofolic acid, and competes with it for the enzyme that catalyzes its conversion to tetrahydrofolic acid
. Resistance to sulfamethoxazole occurs due to a single amino acid substitution in the gene for the dihydropteroate synthase enzyme, dhps.
A homeovitic formulation containing these and other homeopathically prepared nutraceuticals including coenzyme Q10 (CoQ 10), cytochrome C, Sadenosylmethionine (SAM) and tetrahydrofolic acid
had a positive effect on the immune system in a preliminary study that was published in the Journal of Applied Nutrition in 1996.
In addition to individual folate species, we also calculated the ratio of 5C[H.sub.3]THF to TFOL and of reduced folates other than 5C[H.sub.3]THF [non-5C[H.sub.3]THF; sum of 5-formyltetrahydrofolic acid (5CHOTHF), 5,10methenyltetrahydrofolic acid (5,10CH=THF), and tetrahydrofolic acid
(THF)] to TFOL, as described previously (1-5).
The LC-MS/MS measures 5 folate species: 5-methyltetrahydrofolic acid ([5CH.sub.3]THF), FA, 5-formyltetrahydrofolic acid (5CHOTHF), tetrahydrofolic acid
(THF), and 5,10-methenyltetrahydrofolic acid (5,10CH=THF).
The antioxidant molecule vitamin C is known to influence folate synthesis by enhancing formation of the polyglutamate derivatives from tetrahydrofolic acid
and enhancing the transformation of folic acid into tetrahydrofolic acid