Hydrolases are a class of hydrolytic enzymes that divide larger molecules into smaller molecules using water to break the glycosidic bonds. They are present in a wide range of biological interactions in the human body and the natural world. One most obvious example is the presence of hydrolases secreted by Lactobacillus jensenii in the human gut. This stimulates the secretion of bile salts by the liver which aid in the digestion of food. A common examples of hydrolase enzymes might be esterases including phosphatases, glycosidases, lipases, peptidases, and nucleosidases. They are divided into a wide range of subclasses based upon the different bonds they act upon.
Enzymatic hydrolysis of the glycosidic bond takes place via general acid catalysis that requires. Two critical residues are required for this to occur, a nucleophile and a proton donor.
Two major mechanisms give rise to this hydrolysis. Either there is an overall retention, or an inversion of anomeric configuration. In both mechanisms, the position of the proton donor is identical, i.e. within hydrogen-bonding distance of the glycosidic oxygen.
In retaining enzymes, the nucleophilic catalytic base is in close proximity to the sugar anomeric carbon.
Different subclasses of hydrolases have a wide range of different molecular interactions inside the body. Esterases, for example, cleave ester bonds in lipids while phosphatases cleave phosphate groups off molecules. Acetylcholine esterase is a prime example of a crucial esterase. It aids in transforming the neuron impulse into acetic acid. After the impulse, the hydrolase breaks the acetylcholine into choline and acetic acid.
This acetic acid is an important metabolite in the body and a critical intermediate for other bodily reactions like glycolysis. Glycosidases, on the other hand, cleave sugar molecules off carbohydrates and peptidases hydrolyze peptide bonds while lipases hydrolyze glycerides and nucleosidases hydrolyze the bonds of nucleotides.
Hydrolase enzymes have a wide range of functions inside of the body. The degenerative properties of hydrolases, for example, are essential for the body. In lipids, lipases help to facilitate the breakdown of fats, lipoproteins and other larger molecules into smaller molecules like fatty acids and glycerol. These fatty acids and other small molecules are essential in the body’s storage and synthesis of energy.
Hydrolases have a range of structures which dictate their interactions and functions.
Crater / pocket structure topology is most optimal for the recognition of a saccharide non-reducing extremity. It is most commonly encountered in monosaccharides as well as exopolysaccharides such as glucoamylase and β-amylase.
Tunnel structures have only been found in cellobiohydrolases. Nonetheless, the resulting tunnel shapes structure enables a polysaccharide chain to be threaded through it. Thus, the structure allows enzymes to release the product while remaining firmly bound to the polysaccharide chain and create the conditions for processivity.
Groove / cleft structure are “open” structures allow for a random binding of multiple sugar units in polymeric substrates. It is usually found in endo-acting polysaccharidases. Some examples of which might include endocellulases, chitinases, lysozymes and xylanases among others.