水解

Hydrolysis is a chemical reaction in which water is added to a polymer, breaking it into simpler monomer units. During enzyme-assisted hydrolysis, a hydroxyl group binds to one monomer and a hydrogen atom to the other, severing the bond between them. This process reverses dehydration synthesis, which builds large molecules from smaller monomers by removing water.

Hydrolases are enzymes that catalyze hydrolysis reactions by breaking glycosidic bonds between sugar units. Different hydrolases target specific bond types: α-amylase cleaves α-1-4 glycosidic bonds in the middle of starch polymers, while amyloglucosidase breaks only terminal bonds at chain ends. Amylase specifically hydrolyzes amylose into maltose, which maltase further breaks into glucose.

Without sufficient lactase enzyme, lactose cannot be hydrolyzed into glucose and galactose monomers and passes undigested into the colon. Colonic bacteria then metabolize lactose, producing gas and causing water influx. This results in bloating, flatulence, and diarrhea—symptoms of lactose intolerance that can be managed through lactase supplements or dietary changes.

Hydrolysis breaks different polymers into their constituent monomers: peptides hydrolyze into amino acids, carbohydrates into simple sugars, and DNA into nucleotides. The specific monomers released depend on the polymer type and the enzymes involved. These newly released monomers can be repurposed into different polymers via dehydration synthesis based on cellular requirements.

Glycosidic bonds between sugar molecules are inherently unstable and readily susceptible to hydrolysis. Water molecules can attack these bonds, breaking them apart with the help of specific hydrolase enzymes. Different types of glycosidic linkages—such as α-1-4 and α-1-6 bonds in starch—require different hydrolases for efficient cleavage.

Amylose, an unbranched polysaccharide composed of repeating α-glucose monomers, is hydrolyzed by the enzyme amylase using water molecules. This breaks the glycosidic bonds, producing the disaccharide maltose. Maltase then hydrolyzes maltose further into individual glucose units that cells can use for energy or biosynthesis.

Hydrolysis releases monomers from polymers, making them available for cellular reuse. These freed monomers can be reassembled into different polymers through dehydration synthesis, depending on the cell's metabolic needs. This recycling process allows cells to adapt their macromolecular composition without synthesizing all components from scratch.