Defect in vitamin B12 release from lysosomes: newly described inborn error of vitamin B12 metabolism

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Science  14 Jun 1985:
Vol. 228, Issue 4705, pp. 1319-1321
DOI: 10.1126/science.4001945


Cultured diploid fibroblasts from a patient with a previously undescribed inborn error of cobalamin metabolism accumulate unmetabolized, nonprotein-bound vitamin B12 in lysosomes. These cells are able to endocytose the transcobalamin II-B12 complex and to release B12 from transcobalamin II. The freed vitamin B12 is not released from lysosomes into the cytoplasm of the cell. This suggests that there is a specific lysosomal transport mechanism for vitamin B12 in the human.