MetaCyc

Parent Class:

EC-Numbers → 4 -- Lyases → 4.2 -- Carbon-oxygen lyases → 4.2.2 -- Acting on polysaccharides

Synonyms: chondroitinase (ambiguous), chondroitin ABC eliminase (ambiguous), chondroitinase ABC (ambiguous), chondroitin ABC lyase (ambiguous), chondroitin sulfate ABC lyase (ambiguous), ChS ABC lyase (ambiguous), chondroitin sulfate ABC exoeliminase, chondroitin sulfate ABC exolyase, ChS ABC lyase II

Systematic Name: chondroitin-sulfate-ABC exolyase

Unification Links: BRENDA:4.2.2.21, ENZYME:4.2.2.21, IUBMB-ExplorEnz:4.2.2.21

Supersedes EC number: 4.2.2.4

Reaction:
dermatan sulfate_(n) → dermatan sulfate_(n-1) + 4-deoxy-β-D-gluc-4-enuronosyl-(1,3)-N-acetyl-D-galactosamine 4-sulfate,
chondroitin sulfate C_(n) → chondroitin sulfate C_(n-1) + 4-deoxy-β-D-gluc-4-enuronosyl-(1,3)-N-acetyl--D-galactosamine 6-sulfate,
chondroitin sulfate A_(n) → chondroitin sulfate A_(n-1) + 4-deoxy-β-D-gluc-4-enuronosyl-(1,3)-N-acetyl-D-galactosamine 4-sulfate

Enzymes and Genes:
chondroitin sulfate ABC exolyase: ChABCII ( Proteus vulgaris )

Summary:
This reaction is defined as the exolytic cleavage of disaccharide residues from the non-reducing ends of both polymeric chondroitin sulfates and their oligosaccharide fragments.

Please note the diagram is for illustrative purposes only.

The enzyme degrades a variety of glycosaminoglycans of the a chondroitin sulfate and dermatan sulfate containing 4-O-sulfo-N-acetyl-D-galactosamine and L-iduronate 2-O-sulfate-[core protein] type. Chondroitin sulfate, chondroitin-sulfate proteoglycan and dermatan sulfate are the best substrates but the enzyme can also act on hyaluronan at a much lower rate. Keratan sulfate, heparan sulfate and heparin are not substrates. In general, chondroitin sulfate (CS) and dermatan sulfate (DS) chains comprise a linkage region, a chain cap and a repeat region. The repeat region of CS is a repeating disaccharide of glucuronic acid (GlcA) and N-acetylgalactosamine (GalNAc) (-4)GlcA(beta-1 3)GalNAc(beta-1-)(n), which may be O-sulfated on the C-4 and/or C-6 of GalNAc and C-2 of GlcA. GlcA residues of CS may be epimerized to iduronic acid (IdoA) forming the repeating disaccharide (-4)IdoA(alpha-1-3)GalNAc(beta-1-)(n) of DS. Both the concentrations and locations of sulfate-ester substituents vary with glucosaminoglycan source [Huckerby05].

The related enzyme EC 4.2.2.20 has the same substrate specificity but produces a mixture of Delta(4)-unsaturated oligosaccharides of different sizes that are ultimately degraded to Delta(4)-unsaturated tetra- and disaccharides [Hamai97].

Citations: [Yamagata68, Saito68, Suzuki68, Zhang09]