Class II α-mannosidase fromAspergillus fischeri: Energetics of catalysis and inhibition

K.S. Shashidhara, Sushama M. Gaikwad, K.S. Shashidhara, Sushama M. Gaikwad

Index: Int. J. Biol. Macromol. 44(1) , 112-5, (2009)

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Abstract

Energetics of the catalysis of Class II α-mannosidase (E.C.3.2.1.24) from Aspergillus fischeri was studied. The enzyme showed K cat/ K m for Man (α1-3) Man, Man (α1-2) Man and Man (α1-6) Man as 7488, 5376 and 3690 M −1 min −1, respectively. The activation energy, E a was 15.14, 47.43 and 71.21 kJ/mol for α1-3, α1-2 and α1-6 linked mannobioses, respectively, reflecting the energy barrier in the hydrolysis of latter two substrates. The enzyme showed K cat/ K m as 3.56 × 10 5 and 4.61 × 10 5 M −1 min −1 and E a as 38.7 and 8.92 kJ/mol, towards pNPαMan and 4-MeUmbαMan, respectively. Binding of Swainsonine to the enzyme is stronger than that of 1-deoxymannojirimycin.