7-Dehydrocholesterol (7-DHC) is a zoosterol that functions in the serum as a cholesterol precursor, and is photochemically converted to vitamin D3 in the skin, therefore functioning as provitamin-D3. The presence of this compound in human skin enables humans to manufacture vitamin D3 (cholecalciferol). Upon exposure to ultraviolet UV-B rays in the sun light, 7-DHC is converted into vitamin D3 via previtamin D3 as an intermediate isomer. It is also found in the milk of several mammalian species. Lanolin, a waxy substance that is naturally secreted by wool-bearing mammals, contains 7-DHC which is converted into vitamin D by sunlight and then ingested during grooming as a nutrient. In insects 7-dehydrocholesterol is a precursor for the hormone ecdysone, required for reaching adulthood. 7-DHC was discovered by Nobel-laureate organic chemist Adolf Windaus.
Mevalonate kinase deficiency (MKD) is an autosomal recessive metabolic disorder that disrupts the biosynthesis of cholesterol and isoprenoids. It is a rare genetic disorder, but a high frequency is observed in Northern European regions.
RAPADILINO syndrome is an autosomal recessive disorder characterized by:
Neuronal migration protein doublecortin, also known as doublin or lissencephalin-X is a protein that in humans is encoded by the DCX gene.
N-acetylgalactosamine-6-sulfatase is an enzyme that, in humans, is encoded by the GALNS gene.
HSD3B2 is a human gene that encodes for 3beta-hydroxysteroid dehydrogenase/delta(5)-delta(4)isomerase type II or hydroxy-delta-5-steroid dehydrogenase, 3 beta- and steroid delta-isomerase 2. It is expressed principally in steroidogenic tissues and is essential for steroid hormone production. A notable exception is the placenta, where HSD3B1 is critical for progesterone production by this tissue.
Wolframin is a protein that in humans is encoded by the WFS1 gene.
Bifunctional UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase is an enzyme that in humans is encoded by the GNE gene.
Phosphatidylinositol N-acetylglucosaminyltransferase subunit A is the catalytic subunit of the phosphatidylinositol N-acetylglucosaminyltransferase enzyme, which in humans is encoded by the PIGA gene.
Glycine amidinotransferase, mitochondrial is an enzyme that in humans is encoded by the GATM gene.
Sterol-4-alpha-carboxylate 3-dehydrogenase, decarboxylating is an enzyme that in humans is encoded by the NSDHL gene. This enzyme is localized in the endoplasmic reticulum and is involved in cholesterol biosynthesis.
Lathosterol oxidase is a Δ7-sterol 5(6)-desaturase enzyme that in humans is encoded by the SC5D gene.
Oral-facial-digital syndrome 1 protein is a protein that in humans is encoded by the OFD1 gene.
Bardet–Biedl syndrome 2 protein is a protein that in humans is encoded by the BBS2 gene.
Cytochrome c-type heme lyase is an enzyme that in humans is encoded by the HCCS gene on chromosome X.
Desmosterolosis in medicine and biology is a defect in cholesterol biosynthesis. It results in an accumulation of desmosterol and a variety of associated symptoms. Only two cases have been reported as of 2007. The condition is due to inactivating mutations in 24-dehydrocholesterol reductase. Certain anticholesterolemic and antiestrogenic drugs such as triparanol, ethamoxytriphetol, and clomifene have been found to inhibit conversion of desmosterol into cholesterol and to induce desmosterolosis, for instance cataracts.
Hydrops-ectopic calcification-moth-eaten skeletal dysplasia is a defect in cholesterol biosynthesis. Greenberg characterized the condition in 1988.
Yemenite deaf-blind hypopigmentation syndrome is a condition caused by a mutation on the SRY-related HMG-box gene 10.
Laryngo-onycho-cutaneous syndrome is a rare epithelial disorder inherited in an autosomal recessive fashion. It is characterized by abnormalities in the larynx, nails, and skin ("cutaneous"). The disorder is only found in Punjabi Muslims and only a few cases have been reported.
C-5 sterol desaturase is an enzyme that is highly conserved among eukaryotes and catalyzes the dehydrogenation of a C-5(6) bond in a sterol intermediate compound as a step in the biosynthesis of major sterols. The precise structure of the enzyme's substrate varies by species. For example, the human C-5 sterol desaturase oxidizes lathosterol, while its ortholog ERG3 in the yeast Saccharomyces cerevisiae oxidizes episterol.
