Benders'dictionary of nutrition and food technology

497vitamin B 3 Term once used for pantothenic acid and sometimes,incorrectly, used for niacin.vitamin B 4 Name given to what was later identified as a mixtureof the amino acids arginine, glycine and cystine.vitamin B 5 Name given to a substance later presumed to be identicalwith vitamin B 6 or possibly nicotinic acid: also sometimesused for pantothenic acid.vitamin B 6 Generic descriptor for three compounds (chemicallyderivatives of 2-methylpyridine): the hydroxyl (alcohol) compound,pyridoxine (previously known as adermin and pyridoxol);the aldehyde, pyridoxal; and the amine, pyridoxamine; andtheir phosphates. All are equally active biologically. The activemetabolite is pyridoxal 5′-phosphate, which acts as a coenzymein decarboxylation and transamination of amino acids, and inglycogen phosphorylase (EC 2.4.1.1), it also has a role in terminatingthe actions of steroid hormones.Deficiency causes abnormalities in the metabolism of theamino acids tryptophan and methionine; in rats convulsions andskin lesions (acrodynia) and in dairy cows and dogs, anaemiawith abnormal red blood cells. Dietary deficiency leading to clinicalsigns is not known in human beings, apart from a single outbreakin babies fed a severely overheated preparation of formulamilk in the 1950s; they showed abnormalities of amino acidmetabolism and convulsions resembling epileptic seizures, whichresponded to supplements of the vitamin.See also methionine load test; transaminase; tryptophanload test.VITAMIN B 6vitamin B 6 dependency syndromes A very small number of childrensuffer from genetic diseases affecting the binding ofpyridoxal phosphate to just one of the pyridoxal phosphate-