Which of the following is elevated in Pyridoxal Phosphate deficiency?: (A) FIGLU, (B) Homocystine, (C) Methylmalonic acid, (D) Xanthurenic acid
Answer is D. Xanthurenic acid >> Homocysteine (Both are increased in PLP deficiency) 3-OH Kynurenine is one of the intermediate in Tryptophan catabolism Normally conveed to next intermediate and this conversion requires vitamin B6/ PLP. But in B6 deficiency, 3-OH Kynurenine is diveed to form alternate metabolite= Xanthurenic acid (See fig) which is excreted in urine. Homocystine is a chemical compound consisting of two homocysteine molecules joined by a disulfide.