emopamil binding protein (sterol isomerase)

The EBP gene provides instructions for making an enzyme called 3β-hydroxysteroid-Δ8,Δ7-isomerase. This enzyme is responsible for one of the final steps in the production of cholesterol. Specifically, it converts a molecule called 8(9)-cholestenol to lathosterol. Other enzymes then modify lathosterol to produce cholesterol.

Cholesterol is a waxy, fat-like substance that is produced in the body and obtained from foods that come from animals (particularly egg yolks, meat, poultry, fish, and dairy products). Although too much cholesterol is a risk factor for heart disease, this molecule is necessary for normal embryonic development and has important functions both before and after birth. It is a structural component of cell membranes and plays a role in the production of certain hormones and acids used in digestion (bile acids).

More than 55 mutations in the EBP gene have been found to cause X-linked chondrodysplasia punctata 2, a condition that occurs almost exclusively in females and is characterized by bone, skin, and eye abnormalities. Some of the mutations responsible for this condition in females insert or delete a small amount of genetic material from the EBP gene, while others change single protein building blocks (amino acids) in the 3β-hydroxysteroid-Δ8,Δ7-isomerase enzyme. All of these mutations impair the normal function of the enzyme, preventing cells from producing enough cholesterol. A shortage of this enzyme also allows potentially toxic byproducts of cholesterol production to build up in the body. The combination of low cholesterol levels and an accumulation of other substances likely disrupts the growth and development of many body systems. It is not known, however, how this disturbance in cholesterol production leads to the specific features of X-linked chondrodysplasia punctata 2.

Rarely, a severe form of X-linked chondrodysplasia punctata 2 has been reported in males. These cases result from changes involving single amino acids in the 3β-hydroxysteroid-Δ8,Δ7-isomerase enzyme. Affected males have some of the same features as affected females, as well as changes in the structure of the brain, moderately to profoundly delayed development, and other birth defects.

Cytogenetic Location: Xp11.23-p11.22, which is the short (p) arm of the X chromosome between positions 11.23 and 11.22

Molecular Location: base pairs 48,521,776 to 48,528,716 on the X chromosome (Homo sapiens Annotation Release 108, GRCh38.p7) (NCBI)

Cytogenetic Location: Xp11.23-p11.22, which is the short (p) arm of the X chromosome between positions 11.23 and 11.22
  • 3-beta-hydroxysteroid-delta-8,delta-7-isomerase
  • 3-beta-hydroxysteroid-Delta(8),Delta(7)-isomerase
  • CDPX2
  • CPXD
  • D8-D7 sterol isomerase
  • delta(8)-Delta(7) sterol isomerase
  • emopamil-binding protein (sterol isomerase)
  • sterol 8-isomerase