engineering

L-ornithine N5 monooxygenase

L-ornithine N5 monooxygenase is a engineering 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 L-ornithine N5 monooxygenase rather than just read about it. In short: L-ornithine N5 monooxygenase (EC 1.14.13.195 or EC 1.14.13.196) is an enzyme which catalyzes one of the following chemical reactions:L-ornithine + NADPH + O2 ⇌ {\displaystyle \rightleftharpoons } N(5)-hydroxy-L-ornithine + NADP+ + H2O L-ornithine + NAD(P)H + O2 ⇌ {\displaystyle \rightleftharpoons } N(5)-hydroxy-L-ornithine + NAD(P)+ + H2O The three ligands of this enzyme are L-ornithine (substrate), FAD (cofactor)…

Key takeaways

L-ornithine N5 monooxygenase belongs to engineering; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect L-ornithine N5 monooxygenase to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of L-ornithine N5 monooxygenase from memory before moving on to harder problems.

Reference excerpt

L-ornithine N5 monooxygenase (EC 1.14.13.195 or EC 1.14.13.196) is an enzyme which catalyzes one of the following chemical reactions:L-ornithine + NADPH + O2 ⇌ {\displaystyle \rightleftharpoons } N(5)-hydroxy-L-ornithine + NADP+ + H2O L-ornithine + NAD(P)H + O2 ⇌ {\displaystyle \rightleftharpoons } N(5)-hydroxy-L-ornithine + NAD(P)+ + H2O The three ligands of this enzyme are L-ornithine (substrate), FAD (cofactor), and NADPH or NAD(P)H (cofactor and electron donor).

Enzyme classification L-ornithine N5 monooxygenase is classified under two EC numbers - EC1.14.13.195 and EC 1.14.13.196. The first number, 1, identifies the enzyme as an oxidoreductase. The subsequent 14 refers to the fact that this enzyme acts "on paired donors, with incorporation or reduction of molecular oxygen". The 13 identifies this enzyme as using NADH or NAD(P)H as one donor, while incorporating one atom of oxygen onto the other. This is why there are two EC numbers for this enzyme - one ends with 195 referring to NADPH as the donor, while the 196 refers to NAD(P)H as the donor.

Structure L-ornithine N5 monooxygenase adopbts an oxidoreductase Rossmann fold tertiary structure that binds FAD and NADP cofactors. Crystallographic structures have been solved for this class of enzymes from Aspergillus fumigatus. These structures reflect structural changes which take place when the enzyme binds combinations of ligands, including ornithine and NADP. Additional structures have also been solved for strain Af293. These structures reflect different redox and ligation states. The following table briefly describes these crystal structures:

In A. fumigatus, the enzyme is named Af SidA for siderophore biosynthesis protein A. It has three domains for ornithine (substrate), FAD (cofactor), and NAD(P)H (cofactor and electron donor). The enzyme is a homotetramer. N-hydroxylating flavin-containing monooxygenase (NMO) enzymes such as this target the nucleophilic terminal amine groups of primary aliphatic amines such as L-ornithine. The enzyme operates via a multistep oxidative mechanism which has a C4a-hydroperoxyflavin intermediate. SidA stabilizes this intermediate and keeps NADP+ bound throughout the remainder of the catalytic cycle because it is necessary for intermediate stabilization. The nicotinamide-ribose moiety and H-bonding between the main chain and residues Lys107, Asn293, and Ser469 position the L-ornithine alpha carbon such that its side chain amino group can be hydroxylated by the C4a-(hydro)peroxyflavin. Unlike many other NMOs, A. fumigatus SidA strictly acts on ornithine. Interactions with arginine increase interactivity between the reduced flavin and oxygen. The active site is located within a cleft at the interface between the three domains on each subunit. SidA has a resting state (6X0H) in which neither L-ornithine nor NAD(P)H is bound. This resting state has an "out" active site caused by large rotations of the FAD isoalloxazine and a 10-Å movement of the Tyrosine loop. Either flavin reduction or NAD(P)H binding drives the active site to the "in" conformation (6X0I). SidA demonstrates typical kinetics when saturated with L-ornithine. Inhibition is caused by high concentrations of NADPH and NADH. There is an 8-fold increase in catalytic efficiency for NADPH compared to NADH. NADP+ is a competitive inhibitor with respect to NADPH.

Function This enzyme is widely distributed, especially among eukaryotes, being found in Fungi, Metazoa, Protista, Viridiplantae, Choanoflagellates, and Icththyosporeans. Among Bacteria, it is found in Kutzneria sp. 744, and an ornithine hydroxylase from Pseudomonas aeruginosa has a similar structure and 41% amino acid similarity to that of A. nidulans. In addition to being found in the non-pathogenic fungi such as Aspergillus nidulans, it is also found in many fungal pathogens such as Aspergillus fumigatus, Botrytis cinerea, Fusarium oxysporum, Magnaporthe oryzae, Sclerotinia sclerotiorum, Spizellomyces punctatus, and Ustilago maydis. In A. fumigatus, it is classified as a flavoprotein because FAD is a cofactor. It catalyzes the FAD and NADPH-dependent hydroxylation of L-ornithine in biosynthesis of the ferrichrome siderophores triacetylfusarinine and desferriferricrocin. It is produced primarily under iron-limited conditions. Siderophores are also important for virulence. In Kutzneria sp. 744, this enzyme is involved in the biosynthesis of piperazate, which contributes to the biosynthesis of kutzneride antifungal antibiotics.

References

Illustrations

Worked examples

Example 1 — a first encounter with L-ornithine N5 monooxygenase

Start with the simplest possible case. Write down what L-ornithine N5 monooxygenase claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In engineering, 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 L-ornithine N5 monooxygenase 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 L-ornithine N5 monooxygenase 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 L-ornithine N5 monooxygenase

In research: L-ornithine N5 monooxygenase appears in engineering 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 L-ornithine N5 monooxygenase 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: L-ornithine N5 monooxygenase is common in secondary-school and first-year university syllabi. It links to neighbouring topics EC 1.14.13, Enzymes of known structure, so understanding it makes those chapters shorter.
In everyday life: Look for L-ornithine N5 monooxygenase 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 L-ornithine N5 monooxygenase in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what L-ornithine N5 monooxygenase 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 L-ornithine N5 monooxygenase out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is L-ornithine N5 monooxygenase in simple terms?

Why does L-ornithine N5 monooxygenase matter?

Because it connects several engineering 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 L-ornithine N5 monooxygenase?

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 L-ornithine N5 monooxygenase.