pyridoxine 5′-phosphate oxidase is the enzyme that catalyzes the rate-limited step of the b metabolism pathway. vitamin b, which is also known as pyridoxine, is a crucial nutrient for the human body, as it is responsible for more bodily functions than any other vitamin. vitamin b is a coenzyme in the metabolism of carbohydrates, fats and proteins. this means that the enzymes which break these entities down for use in the body cannot function unless vitamin b is present to induce a conformational change in the enzyme, thus activating it. vitamin b also plays a role in the synthesis of hormones, red blood cells, neurotransmitters and enzymes. a person who is deficient in vitamin b could suffer from insomnia, as well as suffer damage to the central nervous system.