Tryptophan load test helps in the evaluation of deficiency of the Vitamin
The synthesis of niacin coenzymes (NAD+ and NADP+) from tryptophan is dependent on PLP The enzyme kynureninase requires PLP. In B6 deficiency, 3-hydroxy anthranilic acid is diveed to xanthurenic acid Increased excretion of xanthurenic acid in urine is an indication of B6 deficiency. ref satyanarayana 4th ed page 145
Folic acid
Niacinamide
Pyridoxine
Cyanocobolamine
vitamins