Enables mannosyl-oligosaccharide 1,2-alpha-mannosidase activity and misfolded protein binding activity. Involved in mannose trimming involved in glycoprotein ERAD pathway; positive regulation of retrograde protein transport, ER to cytosol; and protein targeting to ER. Located in aggresome and endoplasmic reticulum quality control compartment. [provided by Alliance of Genome Resources, Apr 2022]