Partial characterization of murine intestinal maltase-glucoamylase

Using papain digestion together with molecular sieving and ion-exchange HPLC, maltase-glucoamylase (MGA) was purified from small intestinal mucosa of CBA/J mice. The purified enzyme displayed an apparent M.W. of 500-600 kDa by SDS-PAGE analysis and under fully denaturing conditions was found to comprise at least three different glycoproteins with apparent M.W. of 410, 275, and 260 kDa, respectively. Thus, murine MGA displayed structural homology to the enzymes obtained from rat and rabbit intestines and differed substantially from the structures reported for the human, pig, and chicken counterparts. The enzyme showed spontaneous degradation during storage at -20 degrees C with accumulation particularly of the 275 and 260 kDa proteins. In addition, IgG obtained from sera of MGA-deficient CBA/Ca mice previously immunized with murine MGA reacted with the native enzyme, as well as with the 410, 275, and 260 kDa components. These results indicated that the 410 kDa component might constitute a precursor of the components with lower apparent M.W.