Enables hydroxymethylglutaryl-CoA reductase (NADPH) activity. Involved in negative regulation of amyloid-beta clearance; negative regulation of protein catabolic process; and negative regulation of protein secretion. Acts upstream of or within cholesterol biosynthetic process; negative regulation of MAP kinase activity; and visual learning. Predicted to be located in endoplasmic reticulum. Predicted to be active in endoplasmic reticulum membrane and peroxisomal membrane. Is expressed in several structures, including autopod; branchial arch; central nervous system; forelimb bud; and ganglia. Human ortholog(s) of this gene implicated in several diseases, including asthma; coronary artery disease (multiple); dementia; diabetes mellitus (multiple); and neurodegenerative disease (multiple). Orthologous to human HMGCR (3-hydroxy-3-methylglutaryl-CoA reductase). [provided by Alliance of Genome Resources, Apr 2022]