title: Hydrolysis of N-alkyl sulfamates and the catalytic efficiency of an S-N cleaving sulfamidase.
abstract: The final step in the degradation of heparin sulfate involves the enzymatic hydrolysis of its 2-sulfamido groups. To evaluate the power of the corresponding sulfamidases as catalysts, we examined the reaction of N-neopentyl sulfamate at elevated temperatures and found it to undergo specific acid catalyzed hydrolysis even at alkaline pH. A rate constant of 10(-16) s(-1) was calculated using the Eyring equation for water attack on the N-protonated species at pH 7, 25 °C. As a model for the pH neutral reaction, a rate constant for hydroxide attack on (CH(3))(3)CCH(2)N(+)H(2)SO(3)(-) at pH 7, 25 °C was calculated to be 10(-19) s(-1). The corresponding rate enhancement (k(cat)/k(non)) produced by the N-sulfamidase of F. heparinum is approximately 10(16)-fold, which is somewhat larger than those generated by most hydrolytic enzymes but considerably smaller than those generated by S-O cleaving sulfatases.
authors.affiliation: Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
authors.forename: Danielle C
authors.initials: DC
authors.lastname: Lohman
authors.forename: Richard
authors.initials: R
authors.lastname: Wolfenden
authors.forename: David R
authors.initials: DR
authors.lastname: Edwards
mesh_terms: D002384:Catalysis; D006863:Hydrogen-Ion Concentration; D006867:Hydrolases / Q000737:chemistry*; D006868:Hydrolysis; D007700:Kinetics; D015394:Molecular Structure; D013451:Sulfonic Acids / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D013451:Sulfonic Acids; D014867:Water; C005741:sulfamic acid; D006867:Hydrolases; C022708:N-sulfoglucosamine sulfohydrolase