consider-the-metabolic-fate-of-homocysteine-synthesize-a-clear-explanation-which

Question

Consider the metabolic fate of homocysteine: synthesize a clear explanation which single vitamin deficiency (from the B-complex) would most likely cause elevated homocysteine with normal methylmalonic acid (MMA) and why.

Accepted Answer

Vitamin B6 deficiency, because B6-dependent enzymes are required for the transsulfuration pathway that converts homocysteine to cysteine; deficiency raises homocysteine while MMA remains normal.

Answer

Folate deficiency always elevates MMA without changing homocysteine, so it cannot explain elevated homocysteine with normal MMA.

Answer

Vitamin B12 deficiency, because B12 specifically blocks the transsulfuration step leading to isolated homocysteine elevation without affecting MMA.

Answer

Niacin deficiency, because NAD+ shortage directly increases homocysteine synthesis while leaving MMA unaffected.