The sixth mannose is added to the N-glycan precursor. This reaction occurs in the ER lumen and uses a different mannose donor (dolichyl-phosphate-mannose) than the previous steps. It has been proposed that ALG3, along with all the mannosyl- and glucosyltransferases in the N-glycan biosynthesis pathway that use dolichyl-phosphate-mannose or dolichyl-phosphate-glucose as donor, derive from duplications of a common ancestral enzyme (Oriol et al. 2002). Defects in ALG3 are associated with Congenital Disorder of Glycosylation 1D (CDG1D) (Sun et al. 2005).
Mollicone, R, Codogno, P, Oriol, R, Chantret, I, Martinez-Duncker, I
Cohen, J, Chung, WK, Freeze, HH, Wang, C, Eklund, EA, Sun, L
alpha-1,3-mannosyltransferase activity of ALG3 [endoplasmic reticulum membrane]
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