Polysaccharides carbohydrate-based classification

In the following section, enzymes in the EC 2.4 class are presented that catalyze the polymerization of polysaccharides. The Enzyme Commission classification scheme organizes enzymes according to their biochemical function in living systems. Enzymes can, however, also catalyze the reverse reaction which is very often used in biocatalytic synthesis. Therefore newer classification systems have been developed, based on the three-dimensional structure and function of the enzyme, the property of the enzyme, the biotransformation that the enzyme catalyzes etc. [10-15]. The Carbohydrate-Active enZYmes Database [13], which is currently the best database/classification system for carbohydrate active enzymes, uses an amino acid sequence-based classification and would classify some of the enzymes presented in the following as hydrolases rather than transferases (e.g., branching enzyme, sucrases and amylomaltase). Nevertheless we present these enzymes here because they are transferases according to the EC classification. 

The molecules that form the foundation of living systems are often organized into four categories. They are the primary metabolites nucleic acids, proteins, carbohydrates, and lipids. The categories can be grouped together in different ways, based on features that they have in common. For example, nucleic acids, proteins, and polysaccharides are polymeric. Nucleic acids and proteins are further related because they are templated polymers. Other classification systems are also possible.1 Interest in the development of size-expanded versions of biomolecules has grown over the past... 

Natural polymers are broadly classified as polysaccharides, proteins, polynucleotide, and natural rubber. This classification is based on the type of monomer building blocks for the polymer and type of covalent bonds for formation of the polymer. Polysaccharides that are carbohydrate polymers are formed by condensation of monomeric units called monosaccharides, proteins or peptide polymers are formed from amino acids and polynucleotide are synthesized from nucleotide condensation reaction forming glycosidic, peptide, and phosphodiester bonds, respectively. All natural polymers are condensation polymers. 

---