. 2022 May 16;14(5):1057. doi: 10.3390/v14051057

Table 1.

Phage exopolysaccharide depolymerases. Phages carry two types of depolymerases: lyases and hydrolases; this table explains the differences between these two classes with some examples [163,164,165,166,167,168,169,170,171,172,173,174,175,176,177,178,179,180,181,182,183,184,185,186].

Class	Biochemical Activity
Lyases	Break the bonds between carbon with another atom (such as oxygen, sulfur, or another carbon atom) by means other than hydrolysis and oxidation. Phages can contain several different lyases, which break down different exopolysaccharides. Identified lysases include: ●→polysaccharide lyases (act on various polyanionic substrates, cleave a hexose-1,4-alpha- or beta-uronic acid sequence by beta-elimination, yielding products in which the non-reducing terminus is modified to an unsaturated uronic acid); ●→alginate lyases (catalyze the alginate degradation by a beta-elimination mechanism, in which the glycosidic bond between the monomers gets broken, resulting in unsaturated oligosaccharides with a double bond between the C4 and C5 carbons of the sugar rings); ●→exopolygalacturonic acid lyases; ●→guluronan lyases; ●→hyaluronate lyases/hyaluronidases (degradation of hyaluronate); ●→pectate/pectin lyases.
Hydrolases	Cleave a covalent bond by using a water molecule. Bacteriophage hydrolases degrade both bacterial cell walls and exopolysaccharides. Examples of hydrolases of bacteriophages: ●→endorhamnosidases (hydrolysis of O-polysaccharide chain); ●→endosialidases (glycosyl hydrolases that specifically cleave polysialic acid); ●→amylases (glycoside hydrolases); ●→galactosidases (galactoside hydrolases); ●→glucosidases (hydrolases of complex carbohydrates, resulting in monosaccharides); ●→pullulanases (hydrolyses glycosidic bonds of polysaccharides); ●→dextranases (glucosidase); ●→cellulases (hydrolyzes β(1 → 4)-d-glucoside bond of cellulose); ●→sialidases (hydrolyzes the α-linked sialic acid from a variety of molecules, such as oligosaccharides and glycoproteins); ●→xylosidases (catalyze the hydrolysis of α- or β-glycosidic linkages); ●→levanase (hydrolysis of (2 → 6)-beta-D-fructofuranosidic bond in (2 → 6)-beta-D-fructans (levans)).

Class

Biochemical Activity

Lyases

Break the bonds between carbon with another atom (such as oxygen, sulfur, or another carbon atom) by means other than hydrolysis and oxidation. Phages can contain several different lyases, which break down different exopolysaccharides. Identified lysases include:
●→polysaccharide lyases (act on various polyanionic substrates, cleave a hexose-1,4-alpha- or beta-uronic acid sequence by beta-elimination, yielding products in which the non-reducing terminus is modified to an unsaturated uronic acid);
●→alginate lyases (catalyze the alginate degradation by a beta-elimination mechanism, in which the glycosidic bond between the monomers gets broken, resulting in unsaturated oligosaccharides with a double bond between the C4 and C5 carbons of the sugar rings);
●→exopolygalacturonic acid lyases;
●→guluronan lyases;
●→hyaluronate lyases/hyaluronidases (degradation of hyaluronate);
●→pectate/pectin lyases.

Hydrolases

Cleave a covalent bond by using a water molecule. Bacteriophage hydrolases degrade both bacterial cell walls and exopolysaccharides. Examples of hydrolases of bacteriophages:
●→endorhamnosidases (hydrolysis of O-polysaccharide chain);
●→endosialidases (glycosyl hydrolases that specifically cleave polysialic acid);
●→amylases (glycoside hydrolases);
●→galactosidases (galactoside hydrolases);
●→glucosidases (hydrolases of complex carbohydrates, resulting in monosaccharides);
●→pullulanases (hydrolyses glycosidic bonds of polysaccharides);
●→dextranases (glucosidase);
●→cellulases (hydrolyzes β(1 → 4)-d-glucoside bond of cellulose);
●→sialidases (hydrolyzes the α-linked sialic acid from a variety of molecules, such as oligosaccharides and glycoproteins);
●→xylosidases (catalyze the hydrolysis of α- or β-glycosidic linkages);
●→levanase (hydrolysis of (2 → 6)-beta-D-fructofuranosidic bond in (2 → 6)-beta-D-fructans (levans)).