chemistry

Ornithine translocase deficiency

Ornithine translocase deficiency is a chemistry 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 Ornithine translocase deficiency rather than just read about it. In short: Ornithine translocase deficiency, also called hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome, is a rare autosomal recessive urea cycle disorder affecting the enzyme ornithine translocase, which causes ammonia to accumulate in the blood, a condition called hyperammonemia. Ammonia, which is formed when proteins are broken down in the body, is toxic if the levels become too high.

Key takeaways

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

Reference excerpt

Ornithine translocase deficiency, also called hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome, is a rare autosomal recessive urea cycle disorder affecting the enzyme ornithine translocase, which causes ammonia to accumulate in the blood, a condition called hyperammonemia. Ammonia, which is formed when proteins are broken down in the body, is toxic if the levels become too high. The nervous system is especially sensitive to the effects of excess ammonia.

Signs and symptoms

Pathophysiology

Mutations in SLC25A15 cause ornithine translocase deficiency. Ornithine translocase deficiency belongs to a class of metabolic disorders referred to as urea cycle disorders. The urea cycle is a sequence of reactions that occurs in liver cells. This cycle processes excess nitrogen, generated when protein is used by the body, to make a compound called urea that is excreted by the kidneys. The SLC25A15 gene provides instructions for making a protein called a mitochondrial ornithine transporter. This protein is needed to move a molecule called ornithine within the mitochondria (the energy-producing centers in cells). Specifically, this protein transports ornithine across the inner membrane of mitochondria to the region called the mitochondrial matrix, where it participates in the urea cycle. Mutations in the SLC25A15 gene result in a mitochondrial ornithine transporter that is unstable or the wrong shape, and which cannot bring ornithine to the mitochondrial matrix. This failure of ornithine transport causes an interruption of the urea cycle and the accumulation of ammonia, resulting in the signs and symptoms of ornithine translocase deficiency. This disorder is inherited in an autosomal recessive pattern, which means the defective gene is located on an autosome, and two copies of the gene - one from each parent - are required to be born with the disorder. The parents of an individual with an autosomal recessive disorder each carry one copy of the altered gene but do not show signs and symptoms of the disorder.

Diagnosis Clinical findings in HHH syndrome are non-specific. If the disorder is suspected, laboratory testing can provide diagnostic information. Plasma amino acid analysis will show elevated ornithine levels, and urine amino acids will detect homocitrulline. Orotic acid may also be elevated. Ammonia levels can be variably elevated. If these findings are present, molecular testing may provide additional confirmatory information.

Treatment Treatments include discontinuation of protein intake, intravenous infusion of glucose and, as needed, infusion of supplemental arginine and the ammonia removal drugs, sodium phenylacetate and sodium benzoate.

See also Ornithine transcarbamylase deficiency Inborn errors of metabolism Ornithine aminotransferase deficiency (gyrate atrophy of the choroid and retina)

References

Charles Scriver, Beaudet, A.L., Valle, D., Sly, W.S., Vogelstein, B., Childs, B., Kinzler, K.W. (accessed 2007). New York: McGraw-Hill. Summaries of 255 chapters, full text through many universities. There is also the OMMBID blog.

External links

Illustrations

Worked examples

Example 1 — a first encounter with Ornithine translocase deficiency

Start with the simplest possible case. Write down what Ornithine translocase deficiency claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, 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 Ornithine translocase deficiency 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 Ornithine translocase deficiency 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 Ornithine translocase deficiency

In research: Ornithine translocase deficiency appears in chemistry 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 Ornithine translocase deficiency 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: Ornithine translocase deficiency is common in secondary-school and first-year university syllabi. It links to neighbouring topics Amino acid metabolism disorders, Autosomal recessive disorders, Rare diseases, so understanding it makes those chapters shorter.
In everyday life: Look for Ornithine translocase deficiency 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 Ornithine translocase deficiency in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Ornithine translocase deficiency 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 Ornithine translocase deficiency out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Ornithine translocase deficiency in simple terms?

Why does Ornithine translocase deficiency matter?

Because it connects several chemistry 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 Ornithine translocase deficiency?

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 Ornithine translocase deficiency.