# Cytochrome P450scc.

Category: Metabolism

The cytochromes are "pigments," in the same sense that they contain the colored "heme" group that gives hemoglobin its color. P450 means "protein that absorbs light at a wavelength of 450. The scc means "side-chain cleaving," which refers to the removal of the 6 carbon atoms…

4 passages · 1 author · 1989–2013 · Most-cited: [Ray Peat](https://bioenergeticoracle.com/md/voices/ray-peat/index.md)

Canonical page: https://bioenergeticoracle.com/concepts/cytochrome-p450scc

## Synthesis

**Cytochrome P450scc** is the mitochondrial enzyme that catalyzes the rate-limiting step of *steroidogenesis*, cleaving the side chain of cholesterol to form **pregnenolone**. [Source 1, 2] The "scc" designation stands for "side-chain cleaving," referring to the removal of the six carbon atoms that distinguish cholesterol from the first steroid hormone. [Source 1, 2] Peat identified this enzyme as a critical link between energy metabolism and hormonal regulation, noting that its function is vulnerable to inhibition by cyanide, which can be endogenously generated during stress from lipid peroxidation and ammonia. [Source 4] The loss of cytochrome P450scc activity would therefore simultaneously cripple both **respiratory energy production** and the synthesis of protective steroids. [Source 4]

Peat argued that pregnenolone, the product of this enzyme, exerts a stabilizing effect on the cytochrome P-450 family, protecting them against proteolytic degradation and thereby increasing their activity. [Source 3] This stabilization is distinct from the action of cortisol, which promotes the synthesis of these enzymes in moderate amounts but degrades them at higher concentrations. [Source 3] The enzyme's function is also supported by the rhodanese system, which uses sulfane sulfur to detoxify cyanide, chemically restoring the activity of cytochromes that pregnenolone had physically stabilized. [Source 4] Peat reported that supplementing sodium thiosulfate, a sulfur donor for the rhodanese system, improved his tolerance for foods that previously triggered reactions, complementing the protective effects of pregnenolone on the cytochromes. [Source 4]

The enzyme belongs to the broader cytochrome P450 superfamily, which are heme-containing pigments that absorb light at a wavelength of 450 nm and perform crucial detoxifying oxidation reactions, some of which are involved in brain metabolism. [Source 1, 2] Within the brain, Peat noted that **oligodendrocytes**, the glial cells responsible for *myelination*, produce pregnenolone when activated, linking local steroid synthesis by this enzyme to the structural integrity of the nervous system. [Source 2] The activity of cytochrome P450scc is therefore positioned at the intersection of systemic hormonal output, cellular detoxification, and the specialized metabolic demands of neural tissues. [Source 1, 2, 4]

## People also ask

### How does cytochrome P450scc connect energy production to hormone synthesis?

Peat argued that the enzyme is vulnerable to inhibition by cyanide, which can be generated during stress, so its loss would simultaneously cripple respiratory energy production and the synthesis of protective steroids like pregnenolone.

### What role does pregnenolone play in regulating its own synthesis?

Peat argued that pregnenolone stabilizes cytochrome P-450 enzymes against degradation, increasing their activity, which is distinct from cortisol’s effect of promoting synthesis in moderate amounts but causing degradation at higher concentrations.

### How can the rhodanese system support cytochrome P450scc function?

The rhodanese system uses sulfane sulfur to detoxify cyanide, chemically restoring the activity of cytochromes that pregnenolone had physically stabilized, and Peat reported that supplementing the sulfur donor sodium thiosulfate improved his tolerance for problematic foods.

## Related concepts

- [Glial](https://bioenergeticoracle.com/md/concepts/glial/index.md)
- [Metabolic Rate](https://bioenergeticoracle.com/md/concepts/metabolic-rate/index.md)
- [Myelination](https://bioenergeticoracle.com/md/concepts/myelination/index.md)
- [Oligodendrocytes](https://bioenergeticoracle.com/md/concepts/oligodendrocytes/index.md)
- [Pregnenolone](https://bioenergeticoracle.com/md/concepts/pregnenolone/index.md)
- [Thymus Gland](https://bioenergeticoracle.com/md/concepts/thymus-gland/index.md)

## Cited passages

Passage numbers match the `[Source N]` markers in the synthesis above.

### Source 1 — Glossary

Ray Peat · Glossary

> Cytochrome P450scc.
>
> The cytochromes are "pigments," in the same sense that they contain the colored "heme" group that gives hemoglobin its color. P450 means "protein that absorbs light at a wavelength of 450. The scc means "side-chain cleaving," which refers to the removal of the 6 carbon atoms that distinguish cholesterol from pregnenolone. Other Cyt P450 enzymes are important for their detoxifying oxidizing action, and some of these are involved in brain metabolism.

### Source 2 — Multiple Sclerosis and Other Hormone-Related Brain Syndromes

Ray Peat · Article · 2013 · https://raypeat.com/articles/articles/multiple-sclerosis-hormone-related-brain-syndromes.shtml

> 2. Cytochrome P450scc. The cytochromes are \"pigments,\" in the same sense that they contain the colored \"heme\" group that gives hemoglobin its color. P450 means \"protein that absorbs light at a wavelength of 450. The scc means \"side-chain cleaving,\" which refers to the removal of the 6 carbon atoms that distinguish cholesterol from pregnenolone. Other Cyt P450 enzymes are important for their detoxifying oxidizing action, and some of these are involved in brain metabolism.
> 3. Glial means \"glue-like,\" and glial cells are mostly spidery-shaped cells that used to be thought of as just connective, supportive cells in the brain.
> 4. Mitochondria (the \"thread-like bodies\") are the structures in cells which produce most of our metabolic energy by respiration, in response to the thyroid hormones.
> 5. Mucoid--refers to a mucoprotein, a protein which contains some carbohydrate. A glycoprotein; usually not intended as a precise term.
> 6. Myelination. Myelin is a multilayered enclosure of the axons (the long processes) of nerve cells, composed of proteins and complex lipids, including cholesterol. The layered material is a flat, thin extension of the cytoplasm of the oligodendroglial cells.
> 7. Oligodendrocytes are one of the kinds of glial (or neuroglial) cells, and structurally they are unusual in having sheet-like, rather than just thread-like processes; they have a sensitivity (\"receptors\") to stress and valium, and produce pregnenolone when activated. Under the influence of thyroid hormone, they wrap themselves in thin layers around the conductive parts of nerve cells, leaving a multilayered \"myelin\" coating. Their absorption of thyroid hormone is promoted by butyrate, an anti-stress substance found in butter and coconut oil.
> 8. Steroidogenesis is the creation of steroids, usually referring to the conversion of cholesterol to hormones.

### Source 3 — Generative Energy: Restoring the Wholeness of Life

Ray Peat · Book · 1994

> This happened over two years ago, and I hope to visit her city soon to see whether her eyes really became, and stayed, normal. For many years it has been known that steroids, including cholesterol, have an anti-toxic effect. The cytochrome P-450 family of enzymes are an important factor in our resistance to toxins. Moderate amounts of cortisol promote this system, but larger amounts degrade it. Pregnenolone doesn't affect the rate of synthesis of these enzymes, but it stabilizes them against the normal proteolytic enzymes, increasing their activity. I believe this stabilizing action is a general feature of these steroids, explaining other anti-toxic effects such as blocking hemolysis, and probably many features of growth and differentiation, including control of cell division and prevention of atrophy.
>
> After using pregnenolone for several years, I noticed that the slack skin and other signs of aging were coming back. That spring I increased my dose of pregnenolone, and did other things to promote my own pregnenolone synthesis, such as using larger amounts of coconut oil and getting a little more exposure to incandescent light. The effects of the supplements are more noticeable in the summer, since that is when the body's repair processes are greatest. Avoiding the destructive effects of northern winters (without migrating to the south) would seem to require artificial lights as bright as summer daylight.
>
> ### Chapter 12: Restoring Hair Color
>
> Largely because of Albert Szent-Gyorgyi's explorations in biological pigments as factors in cell-regulation and immunity, I have paid special attention to several pigments, such as melanin, the black or brown pigment of hair and skin, of injured potatoes, and of certain fungi, when damaged. When I lived in Montana, I knew many people whose hair became grey in their late I wondered whether it was caused by low thyroid, by an odd mineral balance. by frequent chilling of the skin and scalp, or maybe just by their lack of fresh fruit and vegetables. In Mexico. people in warm, humid tropical areas seldom lost their pigment. When I heard Carl Pfeiffer speak, I noticed that both his skin and his hair were free of pigment, though he was not an albino, and I wondered whether his various mineral nutritional supplements had contributed to his fading. (He took sulfur every day, and avoided copper.

### Source 4 — A New Approach to Detoxifying

Ray Peat · Newsletter · Jan 1989

> The fact that serum albumin, which has many detoxifying functions, carries sulfane sulfur, the form which is used by rhodanese to react with cyanide, supports the idea that rhodanese is involved in the elimination of cyanide.
>
> People who smoke or eat significant amounts of plant material are exposed to cyanide, but the fact that the rhodanese enzyme exists in all animals, whether their diet includes cyanophoric compounds or not, suggests that we might want to consider other possible sources of cyanide.
>
> People studying lipid peroxidation in liver cell extracts noticed that carbon monoxide was being produced. Many people have observed that stressed cells emit ammonia. There are industrial processes which use ammonia and carbon monoxide to produce cyanide, using a metal as catalyst. Since carbon monoxide binds to metal atoms, it might be held in a form which reacts easily with ammonia. Then during stress, which causes both lipid peroxidation and ammonia formation, rhodanese would be needed to protect the respiratory cytochromes from the cyanide, which would otherwise inhibit respiratory energy production, and other processes involving the cytochromes. Within the mitochondria, a cytochrome P-450 converts cholesterol to pregnenolone. The loss of both energy and steroid hormones would have major consequences. Outside the mitochondria, many other cytochrome functions will be inhibited; other types of enzymes would also be inhibited.
>
> Another possible source of cyanide would be bacteria in the intestine; methane and ammonia are other possible starting materials for making cyanide. The urea cycle itself, inside the mitochondria, is a conceivable source.
>
> Even if dietary plant material turns out to be the main source of cyanide, it is important to be able to eliminate it efficiently.
>
> When flowers of sulfur is taken orally, some of it becomes available for use in the rhodanese system. It might be less irritating and more effective to use a form of sulfur which is chemically more available, namely thiosulfate. (My thoughts on light removing carbon monoxide from cytochromes led me to think about photography; sodium thiosulfate is used to clear the photographic emulsion, removing the silver which was not exposed to light. In that sense, its activity as a reductant is equivalent to light's action).

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