This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: vitamins, Subject name: Biochemistry
Which vitamin deficiency causes excretion of xanthurenic acid? 
Select and explain. 
A. Folic acid, B. Pyridoxine, C. Niacin, D. Vitamin B12
B: Pyridoxine
Answer: B: Pyridoxine 
Explanation: Pyridoxine deficiency causes the increased excretion of xanthurenic acid Pyridoxal phosphate is required for the synthesis of niacin from tryptophan.Kylureninase is a dependent enzyme.Hence in Pyridoxine deficiency there is a less production of niacin.Moreover, kylurenine is not conveable fuher which is metabolised to xanthurenic acid and excreted through urine. REFERENCE : DM.VASUDEVAN.Textbook of Biochemistry.6th edition Page no 397