arachidonate 12-lipoxygenase, 12R type
The ALOX12B gene provides instructions for making an enzyme called 12R-LOX. This enzyme is part of a family of enzymes called arachidonate lipoxygenases. Most of these enzymes help add an oxygen molecule to a certain fatty acid called arachidonic acid. The addition of an oxygen molecule to arachidonic acid produces substances called fatty acid hydroperoxides, which can be transformed into a variety of signaling molecules. Specifically, the 12R-LOX enzyme helps add an oxygen molecule to arachidonic acid to make a substance called 12R-hydroperoxyeicosatetraenoic acid (12R-HPETE). 12R-HPETE is later converted to a signaling molecule that is involved in the growth and division (proliferation) and specialization (differentiation) of skin cells.
The 12R-LOX enzyme is thought to play a role in the formation and maintenance of the fat (lipid) membrane of the cells that make up the outermost layer of the skin (the epidermis). The epidermis helps prevent water loss, regulates body temperature, and protects against infection.
More than 30 mutations in the ALOX12B gene have been found to cause nonbullous congenital ichthyosiform erythroderma (NBCIE). Most of these mutations change single protein building blocks (amino acids) in the 12R-LOX enzyme. Many ALOX12B gene mutations lead to the production of a nonfunctional 12R-LOX enzyme, which impairs the formation of the lipid membrane of the cells within the epidermis. Problems with this protective barrier underlie the skin abnormalities and other features of NBCIE.
Another form of ichthyosis called self-healing collodion baby has been found to be caused by ALOX12B gene mutations. Individuals with this condition are born with a tight, clear sheath covering their skin called a collodion membrane. This membrane is usually shed during the first few weeks of life, and affected infants often show near normal skin within a few months.
Only a few people diagnosed with self-healing collodion baby have been found to have ALOX12B gene mutations; the majority of cases are caused by mutations in other genes.
- arachidonate 12-lipoxygenase, 12R-type
- epidermis-type lipoxygenase 12