Hydrolysis of N-alkyl sulfamates and the catalytic efficiency of an S-N cleaving sulfamidase |
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Authors: | Lohman Danielle C Wolfenden Richard Edwards David R |
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Institution: | Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina 27599, USA. |
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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. |
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