the crystalloid endoplasmic reticulum ( er ) consists of hexagonally packed membrane tubules that contain 3-hydroxy-3-methylglutaryl coenzyme a reductase ( hmg coa reductase ) , an intrinsic membrane protein that catalyses the rate-limiting step in cholesterol synthesis .
C0063164
3-hydroxy-3-methylglutaryl coenzyme a reductase
C0020374
hmg coa reductase