Unspecified anomers 58636 , alpha anomer 394282 , beta anomer 388338
Molecular formula C
6H 13O 9P
Molar mass 260.136 g/mol
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Mannose-6-phosphate (M6P) is a molecule bound by lectin in the immune system. M6P is converted to fructose 6-phosphate by mannose phosphate isomerase.
M6P is a key targeting signal for
acid hydrolase precursor proteins that are destined for transport to lysosomes. The M6P tag is added to such proteins in the cis- Golgi apparatus. Specifically, in a reaction involving uridine diphosphate (UDP) and N-acetylglucosamine, the enzyme N-acetylglucosamine-1-phosphate transferase catalyzes the N-linked glycosylation of asparagine residues with M6P. Once appropriately marked with the M6P targeting signal, these proteins are moved to the trans-Golgi network. There, the M6P moiety is recognized and bound by mannose 6-phosphate receptor (MPR) proteins at pH 6.5-6.7. [1 ]
The M6P-tagged lysosomal enzymes are shipped to the late
endosomes via vesicular transport. The pH in the late endosome can reach 6.0, which causes dissociation of M6P from its receptor. [1 ] Upon release, the enzymes are ferried to their final destination in the lysosomes. [1 ] The MPRs are packed into vesicles that bud off the late endosome and return to the "trans"-Golgi network. [1 ] In this way, the MPRs can be recycled. [1 ]
See also [ edit ]
External links [ edit ]
References [ edit ]
^ a b c d e Alberts, Bruce et al. (2002). Molecular biology of the cell (4th ed. ed.). New York: Garland Science. ISBN 0-8153-3218-1.