Absorption, Plasma Transport, and Cellular Retention of Cobalamin Analogues in the Rabbit

Kolhouse, J F; Allen, Robert H.

doi:10.1172/jci108899

Cited by 136 publications

(72 citation statements)

References 34 publications

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“…Our studies have demonstrated that most B12-compound found in spir ulina tablets is pseudo-B12 inactive for humans (19). IF involved in the intestinal absorption of B12 strictly rec ognizes the structure of the B12 molecule (30). Pseudo B12 has been reported to show moderate affinity to IF among various B12-compounds (28).…”

Section: Purification and Characterization Of B12 Compounds From Edibmentioning

confidence: 63%

Characterization and Bioavailability of Vitamin B12-Compounds from Edible Algae.

Watanabe

Takenaka²,

Kittaka-Katsura

et al. 2002

Journal of Nutritional Science and Vitaminology, J Nutr Sci Vit

106

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SummarySubstantial amounts of vitamin B12 were found in some edible algae (green and purple layers) and algal health food (chlorella and spirulina tablets) using the Lactobacillus delbrueckii subsp. lactis ATCC7830 microbiological assay method. Corrinoid compounds were purified and characterized from these algae to clarify the chemical proper ties and bioavailability of the algal vitamin B12. True vitamin B12 is the predominate cobamide of green and purple layers and chlorella tablets. Feeding the purple layer to vita min B12-deficient rats significantly improved the vitamin B12 status. The results suggest that algal vitamin B12 is a bioavailable source for mammals. Pseudovitamin B12 (an inactive cor rinoid) predominated in the spirulina tablets, which are not suitable for use as a vitamin B12 source, especially for vegetarians.

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Section: Purification and Characterization Of B12 Compounds From Edibmentioning

confidence: 63%

Characterization and Bioavailability of Vitamin B12-Compounds from Edible Algae.

Watanabe

Takenaka²,

Kittaka-Katsura

et al. 2002

Journal of Nutritional Science and Vitaminology, J Nutr Sci Vit

106

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“…Radioassays using intrinsic factor from pig stomach are available commercially and allow for rapid determination of 'true vitamin B 12 ' in a large number of samples. Both intrinsic factor and haptocorrin have a high affinity for CBL but haptocorrin has a greater affinity for analogs than intrinsic factor (Kolhouse and Allen, 1977;Adjalla et al, 1993). Measurements of CBL in feed and omasal digesta by LC-MS or by a radioassay using intrinsic factor as binding protein were highly correlated.…”

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confidence: 98%

Supplementing lactating dairy cows with a vitamin B12 precursor, 5,6-dimethylbenzimidazole, increases the apparent ruminal synthesis of vitamin B12

Brito

Chiquette

Stabler

et al. 2015

Animal

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Cobalamin (CBL), the biologically active form of vitamin B 12 , and its analogs, are produced by bacteria only if cobalt supply is adequate. The analogs differ generally by the nucleotide moiety of the molecule. In CBL, 5,6-dimethylbenzimidazole (5,6-DMB) is the base in the nucleotide moiety. The present study aimed to determine if a supplement of 5,6-DMB could increase utilization of dietary cobalt for synthesis of CBL and change ruminal fermentation, nutrient digestibility, omasal flow of nutrients and ruminal protozoa counts. Eight ruminally cannulated multiparous Holstein cows (mean ± standard deviation = 238 ± 21 days in milk and 736 ± 47 kg of BW) were used in a crossover design. Cows were randomly assigned to a daily supplement of a gelatin capsule containing 1.5 g of 5,6-DMB via the rumen cannula or no supplement. Each period lasted 29 days and consisted of 21 days for treatment adaptation and 8 days for data and samples collection. Five corrinoids, CBL and four cobamides were detected in the total mixed ration and the omasal digesta from both treatments. The dietary supplement of 5,6-DMB increased (P = 0.02) apparent ruminal synthesis of CBL from 14.6 to 19.6 (s.e.m. 0.8) mg/day but had no effect (P > 0.1) on apparent ruminal synthesis of the four analogs. The supplement of 5,6-DMB had no effect (P > 0.1) on milk production and composition, or on protozoal count, ruminal pH and concentrations of volatile fatty acids and ammonia nitrogen in rumen content. The supplement had also no effect (P > 0.1) on intake, omasal flow and apparent ruminal digestibility of dry matter, organic matter, NDF, ADF and nitrogenous fractions. Plasma concentration of CBL was not affected by treatments (P = 0.98). Providing a preformed part of the CBL molecule, that is, 5,6-DMB, increased by 34% the apparent ruminal synthesis of CBL by ruminal bacteria but had no effect on ruminal fermentation or protozoa count and it was not sufficient to increase plasma concentrations of the vitamin. Even though the efficiency of cobalt utilization for apparent synthesis of CBL was increased from 2.0% to 2.7% by the 5,6-DMB supplement, this improved efficiency was still very low. Further research is needed to identify the factors affecting efficiency of utilization of cobalt for synthesis of CBL by the bacterial populations in rumen.Keywords: dairy cow, vitamin B 12 , cobalt, 5,6-dimethylbenzimidazole, ruminal microflora ImplicationsUnlike other B vitamins, vitamin B 12 is not present in plants and is produced only by bacteria if cobalt supply is adequate. Therefore, dairy cows rely on synthesis of the vitamin by the bacteria present in rumen to cover their requirements. However, the proportion of cobalt used for these syntheses is low. Providing a preformed part of the vitamin B 12 molecule (5,6-dimethylbenzimidazole) increased by 34% apparent synthesis of the vitamin by ruminal bacteria but failed to increase substantially efficiency of cobalt utilization. The results highlight the lack of knowledge on nutritional factors driving ruminal pr...

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“…Approximately one-quarter of Cbl in plasma is bound to TC, whereas the rest circulates bound to plasmatic HC that can enter only hepatocytes. All three proteins carry a single Cbl molecule and show high affinity to the ligand (6) but differ in specificity for Cbl and its analogues produced by microorganisms (7).…”

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confidence: 99%

Structural basis for mammalian vitamin B ₁₂ transport by transcobalamin

Wuerges

Garau²,

Geremia³

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

166

216

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Cobalamin (Cbl, vitamin B12) serves for two essential cofactors in mammals. The pathway for its intestinal absorption, plasma transport, and cellular uptake uses cell surface receptors and three Cbl-transporting proteins, haptocorrin, intrinsic factor, and transcobalamin (TC). We present the structure determination of a member of the mammalian Cbl-transporter family. The crystal structures of recombinant human and bovine holo-TCs reveal a two-domain architecture, with an N-terminal ␣6-␣6 barrel and a smaller C-terminal domain. One Cbl molecule in base-on conformation is buried inside the domain interface. Structural data combined with previous binding assays indicate a domain motion in the first step of Cbl binding. In a second step, the weakly coordinated ligand H 2O at the upper axial side of added H2O-Cbl is displaced by a histidine residue of the ␣6-␣6 barrel. Analysis of amino acid conservation on TC's surface in orthologous proteins suggests the location of the TC-receptor-recognition site in an extended region on the ␣6-␣6 barrel. The TC structure allows for the mapping of sites of amino acid variation due to polymorphisms of the human TC gene. Structural information is used to predict the overall fold of haptocorrin and intrinsic factor and permits a rational approach to the design of new Cbl-based bioconjugates for diagnostic or therapeutic drug delivery.cobalamin ͉ crystal structure ͉ P259R polymorphism ͉ transport protein

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Absorption, Plasma Transport, and Cellular Retention of Cobalamin Analogues in the Rabbit

Abstract: A B S T R A C T Analogues of cobalamin (

Cited by 136 publications

References 34 publications

Characterization and Bioavailability of Vitamin B12-Compounds from Edible Algae.

Characterization and Bioavailability of Vitamin B12-Compounds from Edible Algae.

Supplementing lactating dairy cows with a vitamin B12 precursor, 5,6-dimethylbenzimidazole, increases the apparent ruminal synthesis of vitamin B12

Structural basis for mammalian vitamin B ₁₂ transport by transcobalamin

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Absorption, Plasma Transport, and Cellular Retention of Cobalamin Analogues in the Rabbit

Abstract: A B S T R A C T Analogues of cobalamin (

Cited by 136 publications

References 34 publications

Characterization and Bioavailability of Vitamin B12-Compounds from Edible Algae.

Characterization and Bioavailability of Vitamin B12-Compounds from Edible Algae.

Supplementing lactating dairy cows with a vitamin B12 precursor, 5,6-dimethylbenzimidazole, increases the apparent ruminal synthesis of vitamin B12

Structural basis for mammalian vitamin B 12 transport by transcobalamin

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Structural basis for mammalian vitamin B ₁₂ transport by transcobalamin