Vitamin B6 (Pyroxidine) is a vital part of the enzyme system and very important to the metabolism of proteins, fats and carbohydrates. It is also vital to the normal function of the nervous and immune systems. The essential amino acid tryptophan also depends on pyroxidine for its utilization. Adequate amounts of riboflavin and niacin are required in the diet for pyroxidine to be used nutritionally.