The function of MAN1A1 (mannosidase alpha class 1A member 1, Ensembl gene identifier ENSG00000111885) is as follows. Involved in the maturation of Asn-linked oligosaccharides. Progressively trim alpha-1,2-linked mannose residues from Man(9)GlcNAc(2) to produce Man(5)GlcNAc(2).