Kinetic isotope effects lysozyme

Kinetic isotope effect for lysozyme. A secondary kinetic isotope effect is expected because a molecule with H in the number 1 position can be converted to the corresponding oxocarbenium ion somewhat more easily than the molecule with 2H in the same position (Eq. 12-13). For example, in the nonenzymatic acid-catalyzed hydrolysis of a methyl- glucoside, a reaction also believed to proceed through a carbocation intermediate,41 75 the ratio h / h, is 1.14 for the a anorner and 1.09 for the (3 anorner.53 In the base-catalyzed hydrolysis of the same compound, which is believed to occur by a double-displacement reaction involving participation of the neighboring OH group on C-2, the ratio /c1h / /c2h is 1.03. The corresponding ratio measured... 

For acid-catalyzed hydrolysis of methyl glucosides53 the kinetic isotope effect observed for the oxygen of the leaving group was /c,6()//c18() = 1.024-1.026. Observation of similar effects for enzymes supports the participation of an acidic group of the protein (Glu 35 of lysozyme) in catalysis but does not eliminate the possibility of concerted involvement of a nucleophilic group, e.g., Asp 52 in lysozyme.81 82... 

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