On the Metabolism of Coenzyme B12

Yagiri, Yoshio

doi:10.5925/jnsv1954.13.197

Cited by 5 publications

(3 citation statements)

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“…This suggestion agrees with the measurement of the coenzyme contents in the liver as reported in the previous paper (22).…”

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confidence: 82%

“…According to the author's experiment in vitamin B12 -deficient rats, both the disappearance from blood and the distribution in tissues of CN-B12 were not so different from those of the normal ones, while the uptake of DBCC was definitely higher in the deficient animals, indicating that the DBCC content in the liver was remarkably decreased, i.e., DBCC is one of the storage form in the liver. From the DBCC activities of the liver and kidneys in the normal, deficient and In the case of the animals injured with carbon tetrachloride, the coenzyme content in the liver was too small to be measured 6 hours after damage as re ported previously (22) and 10 minutes and 3 hours after the measurement the hepatic uptake of CN-B12 and DBCC were found to be smaller than those of the normal ones. Although this finding is against the turnover data for the deficient rats, it seems to be due to the fact that the liver cells have fallen in necrosis on account of the injury produced by carbon tetrachloride.…”

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confidence: 99%

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On the Metabolism of Coenzyme B12

Yagiri¹

1967

J. Vitaminol

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Since coenzyme B12 was fouud by Barker et al. (1) as an active form of vitamin B12 for the first time in 1958, its coenzymic activities have been indicated by many authors (2-8) but its metabolism has not been clarified. From the measurement using radioactive cyanocobalamin (CN-B12), and coenzyme B12 Okuda et al. (9) and Wong et al. (10) reported that the coenzyme had a greater affinity to liver and kidneys than CN-B12. On the basis of the measurement of tissue distribution and urinary and fecal excretion of those cobamides following oral administration, Uchino et al. (11) also indicated that coenzyme B12 had a greater affinity for tissue than CN-B12.Hydroxocobalamin (OH-B12) which was discovered first by Kaczka et al. (12), has attracted attention as one of the long acting derivatives for its retention in blood and affinity to tissues (13,14). It has also been regarded as a natural form of vitamin B12 occurring in the body, but little is known about the correlation between OH-B12 and coenzyme B12.In connection with the relationship between coenzyme B12 and intrinsic factor (IF) it was first suggested that IF had no effect on the absorption of the coenzyme (15), but later was indicated (16) that IF could enhance the absorption of the coenzyme from the gastrointestinal tract. Okuda et al. (17) described that IF administered intravenously with B12 could remarkably enhance the uptake of the vitamin by the liver. There is as yet very little information as to whether IF

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“…This suggestion agrees with the measurement of the coenzyme contents in the liver as reported in the previous paper (22).…”

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confidence: 82%

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confidence: 99%

On the Metabolism of Coenzyme B12

Yagiri¹

1967

J. Vitaminol

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“…Therefore, carbon tetra chloride seems to have a considerable effect on the conversion process from CN -B12 to OH-B12, if the actual process is considered to take place from CN-B12 through OH-B12 to DBCC. This point and the finding of the marked decrease of coenzyme B12 content due to the liver damage as was shown in the previous paper (19), strongly suggest the following possibility. In cartain cases of liver damage the trouble in utilizing B12 is likely to appear in such a way that the vitamin stored in the liver is released into the blood stream, and subsequently the vitamin available in the body becomes poor.…”

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confidence: 49%

On the Metabolism of Coenzyme B12

Yagiri

1967

J. Vitaminol

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Since the coenzyme B12 was discovered as an active form of vitamin B12 (B12) by Barker et al. (1), its biochemical propaties including its coenzymic roles, and its metabolism have been studied in many respects.Today it is considered that vitamin B12 in the liver exists in a coenzyme form (2), 5, 6-dimethyl benzimidazolyl cobamide coenzyme (DBCC), which plays an important role in converting methyl malonyl CoA into succinyl CoA in mammalian cells (3,4).On the other hand, studies on the enzymic biosynthesis of DBCC from B12 derivatives were made by Pawelkiwicz et al. (5) and Bernhauer et al. (6), who showed that the extract of Propionibacterium shermanii could catalyze the con version from aquocobalamin to coenzyme B12 in the presence of ATP and Mg. Barker and Brody et al. (7,8) obtained the enzyme for biosynthesis using the same bacterium and searched for the substrate and cofactor necessary for biosyn thesis. Weissbach and Peterkofsky et al. (9-11) succeeded in the biosynthesis of DBCC using the cell-free extract of Clostridium tetanomorphum.On the other hand, Gorna (12) and Pawelkiwicz et al. (13) reported that the homogenate of liver and kidneys could convert cyanocobalamin (CN-B12) into DBCC in vitro. However, only short reports have been made on the conversion process in the body, of which Fenrych (14) used rabbits, and Martson (15) used the sheep.The present author (16) used animal tissues for the study of fractional deter mination of CN-B12, OH-B12, and DBCC and further studied the conversion process leading to DBCC in the liver and kidneys from 57Co-CN-B12 or 57Co-OH-B12 injected intravenously into rats or human subjects. He also examined the conversion pro cess in vitamin B12-deficient state and in the liver injured by carbon tetrachloride and observed how the conversion process was affected by intrinsic factor (IF) known to promote which is the organ uptake of B12.

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