Lichenase (, ''licheninase'', ''beta-(1->4)-D-glucan 4-glucanohydrolase'', ''1,3, 1,4-beta-glucan endohydrolase'', ''1,3, 1,4-beta-glucan 4-glucanohydrolase'', ''1,3-1,4-beta-D-glucan 4-glucanohydrolase'') is an
enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...
with
systematic name A systematic name is a name given in a systematic way to one unique group, organism, object or chemical substance, out of a specific population or collection. Systematic names are usually part of a nomenclature.
A semisystematic name or semitrivial ...
''(1->3)-(1->4)-beta-D-glucan 4-glucanohydrolase''. It was named after its activity in on
lichenin
Lichenin, also known as lichenan or moss starch, is a complex glucan occurring in certain species of lichens. It can be extracted from ''Cetraria islandica'' (Iceland moss). It has been studied since about 1957.
Structure
Chemically, lichenin i ...
(a form of mixed-linkage glucan).
Activity
This enzyme
catalyses the following
chemical reaction
A chemical reaction is a process that leads to the IUPAC nomenclature for organic transformations, chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the pos ...
:
Hydrolysis
Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile.
Biological hydrolys ...
of β-(1,4)-D-glucosidic linkages in
mixed-linkage glucan Mixed-linkage glucan (MLG), sometimes incorrectly referred to as beta-glucan, is a hemicellulosic polysaccharide consisting of β-D(1-3) and β-D(1-4) linked glucosyl residues. MLG is highly prevalent within the Poales, where it has important prop ...
s containing both (1,3)- and (1,4)-bonds
Specificity
The best-characterised variant of this of enzyme is ''
Bacillus subtilis
''Bacillus subtilis'', known also as the hay bacillus or grass bacillus, is a Gram-positive, catalase-positive bacterium, found in soil and the gastrointestinal tract of ruminants, humans and marine sponges. As a member of the genus ''Bacillus ...
'' lichenase, which is used as a molecular biology tool in determining the structure of mixed-linkage glucans. This variant cleaves (1,4) bonds that immediately follow a (1,3) bond.
Other lichenases have different specificities, for example ''
Aspergillus japonicus'' lichenase cleaves (1,4) bonds that immediately precede a (1,3) bond.
Structure
Lichenases are from
glycoside hydrolase family 16, and share a
jellyroll structure.
A deep surface cleft acts as the
substrate binding site.
References
External links
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