PURIFICATION, CHARACTERIZATION, AND SUBCELLULAR-LOCALIZATION OF SOLUBLE INVERTASE FROM TOMATO FRUIT

Soluble invertase (beta-fructosidase EC 3.2.1.256) was purified to app arent homogeneity from ripe tomato (Lycopersicon esculentum Mill.) fru it using conventional procedures. Soluble tomato invertase is a glycop rotein of 52 kDa with a polypeptide moiety of 45 kDa. This purified en zyme hydrolyzes sucrose to fructose and glucose and raffinose to fruct ose and melibiose. Lycopersicon pimpinellifolium (Jusl.) Mill. fruits also contain an immunologically cross-reactive protein with the same m olecular weight as L. esculentum invertase. Antibodies to deglycosylat ed carrot cell-wall invertase recognized two polypeptides in both toma to species: 52 kDa and 68 kDa. The 52 kDa polypeptides were abundant i n fruit extracts, and the 68 kDa polypeptides were abundant in extract s of suspension culture cells. The 52 kDa invertase is localized in va cuoles of the tomato fruit cells. Amino acid sequence data obtained fr om the 52 kDa polypeptide, two smaller polypeptides (33 kDa and 24 kDa ) believed to be degradation products of the intact protein, and three cyanogen bromide cleavage fragments reveal significant amino acid seq uence similarity with carrot, yeast, and bacterial invertases.