science

Pisatin

Pisatin is a science 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 Pisatin rather than just read about it. In short: Pisatin (3-hydroxy-7-methoxy-4′,5′-methylenedioxy-chromanocoumarane) is the major phytoalexin made by the pea plant Pisum sativum. It was the first phytoalexin to be purified and chemically identified.

Key takeaways

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

Reference excerpt

Pisatin (3-hydroxy-7-methoxy-4′,5′-methylenedioxy-chromanocoumarane) is the major phytoalexin made by the pea plant Pisum sativum. It was the first phytoalexin to be purified and chemically identified. The molecular formula is C17H14O6.

Structure and properties The structure of pisatin consists of a pterocarpan backbone and is distinguishable by the hydroxyl group on the nonaromatic portion of the molecule. This molecule is slightly soluble in water and has high solubility in organic solvents. Pisatin is stable in neutral or slightly basic solutions and loses water in the presence of acid to form anhydropisatin.

Resistance to Pisatin Resistance to pisatin appears to be an important trait for pathogens of Pisum sativum. Detoxification involves the removal of the 3-O-methyl group, which has been shown to reduce the toxicity of the molecule. An enzyme known as pisatin demethylase is responsible for this catalysis and has been identified in N. haematococca as a cytochrome P450 enzyme. Most fungi capable of this metabolism are resistant to pisatin, however, there are some pathogens that do not contain the gene for pisatin demethylase. Such pathogens may have alternative methods for metabolizing phytoalexins. In addition, many microbial species have been found to have the ability to detoxify pisatin, but the most virulent strains have the highest rate of demethylation.

Known resistant fungi N. haematococca Ascochyta pisi Fusarium oxysporum Phoma pinodella Mycosphaerella pinodes Rhizoctonia solani

Biosynthesis The biosynthesis of pisatin begins with the amino acid L-phenylalanine. A deamination reaction then produces trans-cinnamate, which undergoes hydroxylation to form 4-coumarate. Acetyl-CoA is then added to form 4-coumaryl-CoA. Three malonyl-CoA moities are then added and cyclized to introduce a phenol ring. An isomerization reaction then occurs, followed by a hydroxylation and rearrangement of the phenol group to form 2,4′,7-trihydroxyisoflavonone. This molecule can then follow one of two paths, both of which include the loss of water and a methylation to produce formononetin. This product then undergoes hydroxylation to form calycosin, followed by the formation of a dioxolane ring. Another hydroxylation then occurs, followed by an isomerization to form (−)-sopherol. The reduction of a carbonyl to a hydroxyl group and the loss of water then forms (+)-maackiain, which undergoes stereochemical rearrangement and hydroxylation to form (+)-6a-hydroxymaackiain. This molecule is then methylated to yield pisatin.

References

Illustrations

Worked examples

Example 1 — a first encounter with Pisatin

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

In research: Pisatin appears in science 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 Pisatin 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: Pisatin is common in secondary-school and first-year university syllabi. It links to neighbouring topics Benzodioxoles, Phytoalexins, so understanding it makes those chapters shorter.
In everyday life: Look for Pisatin 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 Pisatin in 20 minutes

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

Frequently asked questions

What is Pisatin in simple terms?

Why does Pisatin matter?

Because it connects several science 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 Pisatin?

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 Pisatin.