In vitamin B12 deficiency, folate is trapped in the form of: (A) Formyl THFA, (B) Methenyl THFA, (C) Methyl-THFA, (D) Methylene-THFA
Answer is C. Methylation of homocysteine to methionine is the only way of regeneration of active THFA from methyl THFA. Methionine synthase reaction requires methyl cobalamin. So, deficiency of methyl-B12 leads to trapping of THFA in less utilised methyl-THFA - phenomenon known as folate trap.