title: Synthesis and evaluation of potential inhibitors of chondroitin AC lyase from Flavobacterium heparinum.
abstract: Chondroitin AC lyase from Flavobacterium heparinum degrades chondroitin sulfate glycosaminoglycans via an elimination mechanism, resulting in disaccharides or oligosaccharides with Delta4,5-unsaturated uronic acid residues at their nonreducing end. The syntheses and testing of two potential inhibitors of this lyase are described. Methyl O-(2-acetamido-2-deoxy-beta-D-galactopyranosyl)-(1-->4)-alpha-L-threo-hex-4-enopyranoside, 1, has the trigonal geometry at C5 of the uronic acid moiety expected at the transition state, yet retains the "leaving group" sugar moiety. Surprisingly, compound 1 showed no inhibition of the enzyme. The novel 5-nitro sugar, phenyl (5S)-5-nitro-beta-D-xylopyranoside, 2, is a monosaccharide nitro analogue of the natural substrate, with C5 being a carbon acid of pK(a) 8.8. The rate of reprotonation of the anion generated at this center is sufficiently low that the anion of 2 can be used directly in initial steady-state velocity measurements without significant interference from the conjugate carbon acid. The anion of compound 2 was found to be a competitive inhibitor with a K(i) value of 5 mM, whereas the conjugate acid had a K(i) value of 35 mM.
authors.affiliation: Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia, Canada, V6T 1Z1.
authors.forename: Carl S
authors.initials: CS
authors.lastname: Rye
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Withers
mesh_terms: D002384:Catalysis; D002808:Chondroitin Lyases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D002809:Chondroitin Sulfates / Q000737:chemistry / Q000378:metabolism; D018360:Crystallography, X-Ray; D004187:Disaccharides / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D005417:Flavobacterium / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D011134:Polysaccharides / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism*; D013237:Stereoisomerism; D013997:Time Factors; D014574:Uronic Acids / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism
chemical_list: D004187:Disaccharides; D011134:Polysaccharides; D014574:Uronic Acids; C038142:chondroitin sulfate glycosaminoglycan; C469654:methyl O-(2-acetamido-2-deoxy-beta-D-galactopyranosyl)-(1-4)-alpha-L-threo-hex- 4-enopyranoside; D002809:Chondroitin Sulfates; D002808:Chondroitin Lyases