_Activity and characteristic of maltase from Cotyledons of marrows ( Cucurbita pepo L.)_

 Maltase ( EC: 3.2.1.20 ) was isolated from cotyledons of marrow (Cucurbita pepo L.). The enzymewas partially purified by 80% ammonium sulfate and Sephadex G-50 column chromatography. The optimal pH was 6.0. There are two pKa values at 6.0 and 8.0 indicating that there is histidyl residue taking part in enzyme catalysis. The optimal temperature of the enzyme was 50 ^ᴼC. The activation energy of maltase was 8.0 KJ/mole. The effect of glucose, lactose, maltose, sucrose, starch and dextrin were tested and the enzyme expressed great specificity for maltose . The enzyme did not show any activity with glucose. The two adenosine compounds adenosine monophosphate ( AMP )  and adenosine triphosphate ( ATP ) stimulated maltase activity at both 5mM and 10mM and this may suggest that the maltase-catalyzed reaction is endothermic. Sorbitol, glycerol, sucrose and blue dextran stabilized maltase at 60 ^ᴼC with different rates. Sorbitol was the best stabilizer followed by glycerol.