biology

Nocturnin

Nocturnin 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 Nocturnin rather than just read about it. In short: Nocturnin is a human hydrolase enzyme that is involved in metabolism and its expression is controlled by the rhythmic circadian clock. It is encoded by the NOCT gene located on chromosome 4.

Key takeaways

Nocturnin belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Nocturnin to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Nocturnin from memory before moving on to harder problems.

Reference excerpt

Nocturnin is a human hydrolase enzyme that is involved in metabolism and its expression is controlled by the rhythmic circadian clock. It is encoded by the NOCT gene located on chromosome 4. Nocturnin contains a C-terminal structural domain of the Endonuclease/Exonuclease/phosphatase family. A study in January 2019, demonstrated that NADP+ and NADPH are the direct targets of Nocturnin. The Drosophila melanogaster ortholog of Nocturnin is Curled. Knockouts of Curled lead to the curled wing phenotype in fruit flies. The curled wing phenotype was first discovered by Thomas Hunt Morgan in 1915. In mice the Nocturnin ortholog is responsible for controlling diet and weight-gain, knockout mice do not gain weight when placed on a high-fat diet, when compared to normal mice containing Nocturnin. In mice it has also been shown that Nocturnin is rhythmically expressed even when mice are placed in complete darkness, demonstrating that Nocturnin expression is driven by our body's internal clock.

Cellular localization Nocturnin was shown to have a Mitochondrial targeting sequence, which is located on the N-terminus of the protein. The targeting sequence of Nocturnin is cleaved off at the mitochondria to allow entry.

Enzymatic activity Nocturnin was previously thought to deadenylate mRNAs of metabolic genes, but two studies in 2018 found that Nocturnin does not directly possess ribonuclease activity. A study in January 2019 demonstrated that human Nocturnin is a phosphatase that acts directly on NADP(H) to remove the 2' phosphate. Curled, the Drosophila ortholog, was also shown to be an NADP(H) 2' phosphatase, which indicates that the enzymatic activity is conserved from humans to fruit flies.

Structure Nocturnin contains a C-terminal structural domain of the Endonuclease/Exonuclease/phosphatase family (EEP). Its protein fold is similar to that of DNase I, AP endonuclease, INPP5B, Sphingomyelin phosphodiesterase, TDP2, PDE12, and CNOT6L. As in the other EEP members, five conserved catalytic residues help coordinate a Magnesium atom, for Nocturnin the divalent metal participates in the NADP(H) phosphatase activity. The first structures of human Nocturnin were solved in 2017-2018 (6BT1, 6BT2, and 6MAL). All three were of the C-terminal EEP-like domain of Nocturnin bound to its cofactor magnesium. In December 2018, the first structure of Nocturnin bound to its natural substrate, NADPH, was determined, 6NF0.

References

External links Overview of all the structural information available in the PDB for UniProt: Q9UK39 (Nocturnin) at the PDBe-KB.

Illustrations

Worked examples

Example 1 — a first encounter with Nocturnin

Start with the simplest possible case. Write down what Nocturnin 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 Nocturnin 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 Nocturnin 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 Nocturnin

In research: Nocturnin 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 Nocturnin 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: Nocturnin is common in secondary-school and first-year university syllabi. It links to neighbouring topics Enzymes of known structure, Genes on human chromosome 4, so understanding it makes those chapters shorter.
In everyday life: Look for Nocturnin 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 Nocturnin in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Nocturnin means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Nocturnin out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Nocturnin in simple terms?

Nocturnin is a human hydrolase enzyme that is involved in metabolism and its expression is controlled by the rhythmic circadian clock. It is encoded by the NOCT gene located on chromosome 4.

Why does Nocturnin 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 Nocturnin?

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 Nocturnin.