Biotin nutritional requirement

Biotin 515, 516,711, 721, 723 - 730,723s biosynthesis of 718, 745 in enzymes, table 724 mechanism of action 725 - 729 nutritional requirement 756 Biotin-binding proteins 728 Biotin carboxylase 724 Biotin carboxyl carrier protein 724 Biotin holoenzyme synthetase 724... 

FIGURE 3.10 Structure of queuosine. Queuosine is incorporated into certain types of transfer RNA. The importance of queunosine to human health is not certain. A great quantity of compoimds are s)mthesized by the gut microflora, including vitamin B12, vitamin K, and biotin (a vitamin). In some cases, these sources of vitamin contribute to the nutritional requirements of the host animal. Essentially all of otir vitamin 612 is acquired from bacteria, but indirectly via meat. Beef cattle acquire their vitamin Bj2 from their gut bacteria, and people, in turn, acquire this vitamin from meat. 

FIGURE 4, Duplication strains of A. nidulans. Linkage groups I and II are shown by unbroken and broken lines, respectively. Symbols O, centromere y, recessive mutant allele determining yellow conidia ad, bi, recessive mutant alleles determining requirements, respectively, for adenine and biotin. Deletion of dominant alleles produces sectors differing from the parent in conidial color or nutritional requirements. 

MINERAL AND VITAMIN SUPPLEMENTS. There is considerable controversy among nutritionists and pediatricians regarding the amounts and types of nutrient supplements that are required by infants, since breast-fed infants have long been given little or no supplementation. Furthermore, the need for supplementation depends upon a variety of factors such as (1) status of the infant at birth, since preterm or low birth weight infants have higher nutritional requirements to attain the rates of growth and development of normal infants (2) type of milk or formula used (3) affliction of the infant with diarrhea, fever, infection, and/or other stresses and (4) age at which supplemental foods are introduced. It is noteworthy that even breast milk is low in iron, copper, fluoride, vitamins A, D, and E, and biotin, folacin, niacin, thiamin, and vitamin B-6. Furthermore, diluted evaporated milk is notably inferior to breast milk with respect to the contents of iron, zinc, vitamin A, vitamin E, and vitamin C. Therefore, the need for nutrient supplements should be evaluated by a health professional who is familiar with the diet and the overall health status of the infant. 

Explanation (b) above may of course explain the behavior of group 2, but the whole picture is more consistent with mcplanation (a) in which the nutritional requirements reflect an increasing power to synthesize biotin in proceeding from group 1 to group 3. 

Growth-inhibitions by compounds structurally related to biotin have been observed. These are different in kind from the action of the antibiotin factor, where an inactive protein complex is formed. These structurally related anti-metabolites include biotin sulfone and desthiobiotin, their activities being related to the nutritional requirements of the organ-... 

It is apparent that at this stage of development definitive conclusions are premature, and that this aspect of amino acid and lipide metabolism will be pursued vigorously in the near future. It is of considerable interest to us that biotin and pantothenic acid deficiencies affect amino acid transport in L. arabinosus, since both vitamins are known to play a prominent role in lipide biosynthesis. We are currently reexamining the turnover of lipide fractions in nutritionally normal and vitamin-deficient cell types to determine whether there is some relation between this aspect of metabolism and amino acid transport. In any case, the nature of the catalytic steps involved in amino acid transport is still unknown to us. They probably occur in the peripheral cell membrane, but even this elementary and widely accepted belief will require additional study before it can be accepted beyond doubt as an established fact. 

More recently, similar signs of biotin deficiency have been observed in patients receiving total parenteral nutrition for prolonged periods, after major resection of the gut. The signs resolve after the provision of biotin, but again there have been no studies of the amounts of biotin required intakes have ranged between 60 to 200 /xg per day (Mock et al., 1985). 

In the investigation of vitamin deficiencies, it is well to bear in mind that diets deficient in a rangle vitamin produce metabolic disorders which alter the animal s requirement for other nutritional factors. Where pantothenic acid deficiency is concerned, there is evidence that the metabolism of ascorbic acid, biotin, protein, carbohydrate, and fat are involved. 

Mock, D.M., 2004. Biotin physiology, dietary sources and requirements. In Caballero, B., Allen, L., and Prentice, A. (ed.) Encyclopaedia of Human Nutrition 2nd ed. Academic Press, London, UK 206-209. 

Zempleni, J., and Mock, D.M., 1999a. Biotin biochemistry and human requirements. The Journal of Nutritional Biochemistry. 10 128 138. 

Biotin, the anti-egg white injury factor, is presumably needed in human nutrition, but requirement would be difficult to establish. The intestinal bacteria synthesize this factor, and the average diet appears to supply... 

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