biology

Inositol-3-phosphate synthase

Inositol-3-phosphate synthase 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 Inositol-3-phosphate synthase rather than just read about it. In short: In enzymology, an inositol-3-phosphate synthase (EC 5.5.1.4) is an enzyme that catalyzes the chemical reaction D-glucose 6-phosphate ⇌ {\displaystyle \rightleftharpoons } 1D-myo-inositol 3-phosphate Hence, this enzyme has one substrate, D-glucose 6-phosphate, and one product, 1D-myo-inositol 3-phosphate. This enzyme belongs to the family of isomerases, specifically the class of intramolecular lyases.

Key takeaways

Inositol-3-phosphate synthase belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Inositol-3-phosphate synthase to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Inositol-3-phosphate synthase from memory before moving on to harder problems.

Reference excerpt

In enzymology, an inositol-3-phosphate synthase (EC 5.5.1.4) is an enzyme that catalyzes the chemical reaction

D-glucose 6-phosphate ⇌ {\displaystyle \rightleftharpoons } 1D-myo-inositol 3-phosphate Hence, this enzyme has one substrate, D-glucose 6-phosphate, and one product, 1D-myo-inositol 3-phosphate. This enzyme belongs to the family of isomerases, specifically the class of intramolecular lyases. The systematic name of this enzyme class is 1D-myo-inositol-3-phosphate lyase (isomerizing). Other names in common use include myo-inositol-1-phosphate synthase, D-glucose 6-phosphate cycloaldolase, inositol 1-phosphate synthatase, glucose 6-phosphate cyclase, inositol 1-phosphate synthetase, glucose-6-phosphate inositol monophosphate cycloaldolase, glucocycloaldolase, and 1L-myo-inositol-1-phosphate lyase (isomerizing). This enzyme participates in streptomycin biosynthesis and inositol phosphate metabolism. It employs one cofactor, NAD+. The reaction this enzyme catalyses represents the first committed step in the production of all inositol-containing compounds, including phospholipids, either directly or by salvage. The enzyme exists in a cytoplasmic form in a wide range of plants, animals, and fungi. It has also been detected in several bacteria and a chloroplast form is observed in alga and higher plants. Inositol phosphates play an important role in signal transduction. In Saccharomyces cerevisiae (Baker's yeast), the transcriptional regulation of the INO1 gene encoding inositol-3-phosphate synthase has been studied in detail and its expression is sensitive to the availability of phospholipid precursors as well as growth phase. The regulation of the structural gene encoding 1L-myo-inositol-1-phosphate synthase has also been analyzed at the transcriptional level in the aquatic angiosperm, Spirodela polyrrhiza (Giant duckweed) and the halophyte, Mesembryanthemum crystallinum (Common ice plant). In prokaryotes, myo-D-inositol phosphate synthase was discovered by Bachhawat and Mande in 1999 (reported in Journal of Molecular Biology). The existence of inositol in prokaryotes is not extensive, but the discovery of this enzyme first in Mycobacterium tuberculosis, nucleated activity towards finding its inhibitors.

Structural studies As of late 2007, 12 structures have been solved for this class of enzymes, with PDB accession codes PDB: 1GR0, PDB: 1JKF, PDB: 1JKI, PDB: 1LA2, PDB: 1P1F, PDB: 1P1H, PDB: 1P1I, PDB: 1P1J, PDB: 1P1K, PDB: 1RM0, PDB: 1VJP, and PDB: 1VKO.

References

Further reading Eisenberg F Jr (1967). "D-myoinositol 1-phosphate as product of cyclization of glucose 6-phosphate and substrate for a specific phosphatase in rat testis". J. Biol. Chem. 242 (7): 1375–82. doi:10.1016/S0021-9258(18)96102-8. PMID 4290245. Sherman WR, Stewart MA, Zinbo M (1969). "Mass spectrometric study on the mechanism of D-glucose 6-phosphate-L-myo-inositol 1-phosphate cyclase". J. Biol. Chem. 244 (20): 5703–8. doi:10.1016/S0021-9258(18)63616-6. PMID 4310603. Barnett JE, Corina DL (1968). "The mechanism of glucose 6-phosphate-D-myo-inositol 1-phosphate cyclase of rat testis. The involvement of hydrogen atoms". Biochem. J. 108 (1): 125–9. doi:10.1042/bj1080125. PMC 1198777. PMID 4297937. Barnett JE, Rasheed A, Corina DL (1973). "Partial reactions of D-glucose 6-phosphate-1L-myoinositiol 1-phosphate cyclase". Biochem. J. 131 (1): 21–30. doi:10.1042/bj1310021. PMC 1177435. PMID 4352864. Bachhawat N and Mande SC (1999) J. Mol. Biol. Identification of the INO1 gene of Mycobacterium tuberculosis H37Rv reveals a novel class of inositol-1-phosphate synthase enzyme. 291, 531–536.

Illustrations

Worked examples

Example 1 — a first encounter with Inositol-3-phosphate synthase

Start with the simplest possible case. Write down what Inositol-3-phosphate synthase 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 Inositol-3-phosphate synthase 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 Inositol-3-phosphate synthase 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 Inositol-3-phosphate synthase

In research: Inositol-3-phosphate synthase 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 Inositol-3-phosphate synthase 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: Inositol-3-phosphate synthase is common in secondary-school and first-year university syllabi. It links to neighbouring topics EC 5.5.1, Enzymes of known structure, Isomerase stubs, so understanding it makes those chapters shorter.
In everyday life: Look for Inositol-3-phosphate synthase 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 Inositol-3-phosphate synthase in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Inositol-3-phosphate synthase 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 Inositol-3-phosphate synthase out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Inositol-3-phosphate synthase in simple terms?

In enzymology, an inositol-3-phosphate synthase (EC 5.5.1.4) is an enzyme that catalyzes the chemical reaction D-glucose 6-phosphate ⇌ {\displaystyle \rightleftharpoons } 1D-myo-inositol 3-phosphate Hence, this enzyme has one substrate, D-glucose 6-phosphate, and one product, 1D-myo-inositol 3-phos…

Why does Inositol-3-phosphate synthase 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 Inositol-3-phosphate synthase?

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 Inositol-3-phosphate synthase.