science

Ligase

Ligase 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 Ligase rather than just read about it. In short: In biochemistry, a ligase is an enzyme that can catalyze the joining (ligation) of two molecules by forming a new chemical bond. This is typically via hydrolysis of a small pendant chemical group on one of the molecules, typically resulting in the formation of new C-O, C-S, or C-N bonds.

Key takeaways

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

Reference excerpt

In biochemistry, a ligase is an enzyme that can catalyze the joining (ligation) of two molecules by forming a new chemical bond. This is typically via hydrolysis of a small pendant chemical group on one of the molecules, typically resulting in the formation of new C-O, C-S, or C-N bonds. For example, DNA ligase can join two complementary fragments of nucleic acid by forming phosphodiester bonds, and repair single-stranded breaks that arise in double stranded DNA during replication. In general, a ligase catalyzes the following dehydration reaction, thus joining molecules A and B: A-OH + B-H → A–B + H2O

Nomenclature The naming of ligases is inconsistent and so these enzymes are commonly known by several different names. Generally, the common names of ligases include the word "ligase", such as in DNA ligase, an enzyme commonly used in molecular biology laboratories to join together DNA fragments. However, many common names use the term "synthetase" or "synthase" instead, because they are used to synthesize new molecules. There are also some ligases that use the name "carboxylase" to indicate that the enzyme specifically catalyzes a carboxylation reaction. To note: biochemical nomenclature has sometimes distinguished synthetases from synthases and sometimes treated the words as synonyms. Commonly, the two terms are used interchangeably and are both used to describe ligases.

Classification Ligases are classified as EC 6 in the EC number classification of enzymes. Ligases can be further classified into six subclasses:

EC 6.1 includes ligases used to form carbon-oxygen bonds EC 6.2 includes ligases used to form carbon-sulfur bonds EC 6.3 includes ligases used to form carbon-nitrogen bonds (including argininosuccinate synthetase) EC 6.4 includes ligases used to form carbon-carbon bonds, such as acetyl-CoA carboxylase EC 6.5 includes ligases used to form phosphoric ester bonds, such as DNA ligase EC 6.6 includes ligases used to form nitrogen-metal bonds, as in the chelatases

Membrane-associated ligases Some ligases associate with biological membranes as peripheral membrane proteins or anchored through a single transmembrane helix, for example certain ubiquitin ligase related proteins.

Etymology and pronunciation The word ligase uses combining forms of lig- (from the Latin verb ligāre, "to bind" or "to tie together") + -ase (denoting an enzyme), yielding "binding enzyme".

Illustrations

Worked examples

Example 1 — a first encounter with Ligase

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

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

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

Frequently asked questions

What is Ligase in simple terms?

Why does Ligase 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 Ligase?

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 Ligase.