biology

Lanosterol 14 alpha-demethylase

Lanosterol 14 alpha-demethylase is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Lanosterol 14 alpha-demethylase rather than just read about it. In short: Lanosterol 14α-demethylase (CYP51A1) is the animal version of a cytochrome P450 enzyme that is involved in the conversion of lanosterol to 4,4-dimethylcholesta-8(9),14,24-trien-3β-ol. The cytochrome P450 isoenzymes are a conserved group of proteins that serve as key players in the metabolism of organic substances and the biosynthesis of important steroids, lipids, and vitamins in eukaryotes.

Key takeaways

Lanosterol 14 alpha-demethylase belongs to biology; place it in that map before memorising details.
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Reproduce the core statement of Lanosterol 14 alpha-demethylase from memory before moving on to harder problems.

Reference excerpt

Lanosterol 14α-demethylase (CYP51A1) is the animal version of a cytochrome P450 enzyme that is involved in the conversion of lanosterol to 4,4-dimethylcholesta-8(9),14,24-trien-3β-ol. The cytochrome P450 isoenzymes are a conserved group of proteins that serve as key players in the metabolism of organic substances and the biosynthesis of important steroids, lipids, and vitamins in eukaryotes. As a member of this family, lanosterol 14α-demethylase is responsible for an essential step in the biosynthesis of sterols. In particular, this protein catalyzes the removal of the C-14α-methyl group from lanosterol. This demethylation step is regarded as the initial checkpoint in the transformation of lanosterol to other sterols that are widely used within the cell.

Evolution

The structural and functional properties of the cytochrome P450 superfamily have been subject to extensive diversification over the course of evolution. Recent estimates indicate that there are currently 267 families of CYP proteins participating in 10 classes of P450 electron transport systems. It is believed that 14α-demethylase or CYP51 diverged early in the cytochrome's evolutionary history and has preserved its function ever since; namely, the removal of the 14α-methyl group from sterol substrates. Although CYP51's mode of action has been well conserved, the protein's sequence varies considerably between biological kingdoms. CYP51 sequence comparisons between kingdoms reveal only a 22-30% similarity in amino acid composition.

Structure

Although the structure of 14α-demethylase may vary substantially from one organism to the next, sequence alignment analysis reveals that there are six regions in the protein that are highly conserved in eukaryotes. These include residues in the B' helix, B'/C loop, C helix, I helix, K/β1-4 loop, and β-strand 1-4 that are responsible for forming the surface of the substrate binding cavity. Homology modeling reveals that substrates migrate from the surface of the protein to the enzyme's buried active site through a channel that is formed in part by the A' alpha helix and the β4 loop. Finally, the active site contains a heme prosthetic group in which the iron is tethered to the sulfur atom on a conserved cysteine residue. This group also binds diatomic oxygen at the sixth coordination site, which is eventually incorporated onto the substrate.

Mechanism

The enzyme-catalyzed demethylation of lanosterol is believed to occur in three steps, each of which requires one molecule of diatomic oxygen and one molecule of NADPH (or some other reducing equivalent). During the first two steps, the 14α-methyl group undergoes typical cytochrome monooxygenation in which one oxygen atom is incorporated by the substrate and the other is reduced to water, resulting in the sterol's conversion to a carboxyalcohol and then a carboxyaldehyde. The aldehyde then departs as formic acid and a double bond is simultaneously introduced to yield the demethylated product.

See also Steroidogenic enzyme Azole antifungals

References

Illustrations

Worked examples

Example 1 — a first encounter with Lanosterol 14 alpha-demethylase

Start with the simplest possible case. Write down what Lanosterol 14 alpha-demethylase claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Lanosterol 14 alpha-demethylase before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Lanosterol 14 alpha-demethylase ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Lanosterol 14 alpha-demethylase

In research: Lanosterol 14 alpha-demethylase appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Lanosterol 14 alpha-demethylase in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Lanosterol 14 alpha-demethylase is common in secondary-school and first-year university syllabi. It links to neighbouring topics Cytochrome P450, EC 1.14.14, Enzymes of known structure, so understanding it makes those chapters shorter.
In everyday life: Look for Lanosterol 14 alpha-demethylase outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Lanosterol 14 alpha-demethylase in 20 minutes

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Frequently asked questions

What is Lanosterol 14 alpha-demethylase in simple terms?

Why does Lanosterol 14 alpha-demethylase matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Lanosterol 14 alpha-demethylase?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Lanosterol 14 alpha-demethylase.