In biochemistry, a ligase is an enzyme that can catalyze the joining (ligation) of two large molecules by forming a new chemical bond. This is typically via hydrolysis of a small pendant chemical group on one of the larger molecules or the enzyme catalyzing the linking together of two compounds, e.g., enzymes that catalyze joining of C-O, C-S, C-N, etc. In general, a ligase catalyzes the following reaction:
or sometimes
where the lowercase letters can signify the small, dependent groups. Ligase can join two complementary fragments of nucleic acid and repair single stranded breaks that arise in double stranded DNA during replication.
The common names of ligases often include the word "ligase", such as DNA ligase, an enzyme commonly used in molecular biology laboratories to join together DNA fragments. Other common names for ligases include the word "synthetase", because they are used to synthesize new molecules.
Biochemical nomenclature has sometimes distinguished synthetases from synthases and sometimes treated the words as synonyms. Under one definition, synthases do not use energy from nucleoside triphosphates (such as ATP, GTP, CTP, TTP, and UTP), whereas synthetases do use nucleoside triphosphates. It is also said that a synthase is a lyase (a lyase is an enzyme that catalyzes the breaking of various chemical bonds by means other than hydrolysis and oxidation, often forming a new double bond or a new ring structure) and does not require any energy, whereas a synthetase is a ligase (a ligase is an enzyme that binds two chemicals or compounds) and thus requires energy. However, the Joint Commission on Biochemical Nomenclature (JCBN) dictates that "synthase" can be used with any enzyme that catalyses synthesis (whether or not it uses nucleoside triphosphates), whereas "synthetase" is to be used synonymously. [1]
Ligases are classified as EC 6 in the EC number classification of enzymes. Ligases can be further classified into six subclasses:
Some ligases associate with biological membranes as peripheral membrane proteins or anchored through a single transmembrane helix, [2] for example certain ubiquitin ligase related proteins.
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".
Nucleotides are organic molecules consisting of a nucleoside and a phosphate. They serve as monomeric units of the nucleic acid polymers deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both of which are essential biomolecules within all life-forms on Earth. Nucleotides are obtained in the diet and are also synthesized from common nutrients by the liver.
In biochemistry, a lyase is an enzyme that catalyzes the breaking of various chemical bonds by means other than hydrolysis and oxidation, often forming a new double bond or a new ring structure. The reverse reaction is also possible. For example, an enzyme that catalyzed this reaction would be a lyase:
Hydrolase is a class of enzyme that commonly perform as biochemical catalysts that use water to break a chemical bond, which typically results in dividing a larger molecule into smaller molecules. Some common examples of hydrolase enzymes are esterases including lipases, phosphatases, glycosidases, peptidases, and nucleosidases.
In biochemistry, a synthase is an enzyme that catalyses a synthesis process.
Purine metabolism refers to the metabolic pathways to synthesize and break down purines that are present in many organisms.
Guanosine monophosphate synthetase, also known as GMPS is an enzyme that converts xanthosine monophosphate to guanosine monophosphate.
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