Carbohydrate moieties were released from human thyroglobulins prepared from normal and transformed, thyroid tissues by hydrazinolysis. The oligosaccharides thus prepared were fractionated by DEAE-cellulose, Bio-Gel P-4, concanavalin-A -Sepharose and Ricinus-conimurzis-agglutinin -Sepharose columns and were characterized by exo-glycosidase and endo-glycosidase digestions, methylation analysis and 400-MHz 'H-NMR spectroscopy.These studies showed that the alterations accompanying malignancy occurred in complex-type carbohydrate chains and exhibited the following structural features : (a) a complex-type carbohydrate chain containing 1 phosphate in a diester linkage was present in all the malignant thyroglobulins. (b) Asialo-carbohydrate chains with biosynthetically incomplete structures were found in all of the malignant thyroglobulins. (c) Carbohydrate chains of higher molecular mass, which have repeating Gal-GlcNAc disaccharides and peripheral a-fucosyl residues were present in metastatic papillary carcinoma.The changes in cell-surface membrane proteins and lipids accompanying malignant transformation have been intensively studied [I -41. One of the characteristic alterations associated with malignant transformation is the appearance or increase of fucosyl glycopeptides of apparently large molecular mass [5 -121. This phenomenon was found when the glycopeptide mixtures obtained from the surface of normal and transformed cells by proteolytic cleavage were analyzed by gel filtration. From the results of neuraminidase treatment or mild acid hydrolysis, a higher content of sialic acid in the glycopeptides was said to be responsible for the increase of molecular mass of the glycopeptides from malignantly transformed cells [8, 131. However, no detailed structural analysis has been performed to confirm this assumption, because the complex nature of the peptide moieties of the glycopeptides hampered the isolation of a single glycopeptide in sufficient quantity for structural study. Recently, a hydrazinolysis technique has been employed to release the carbohydrate moieties from glycoproteins [14]. In this paper, this technique was applied to human thyroglobulins (19 S) purified from normal and transformed thyroid glands and the structural changes of the carbohydrate chains of human thyroglobulin accompanying oncogenic transformation of the human thyroid gland were examined.Abbreviations. ConA, concanavalin A; GlcNAcol, 2-acetamido-2-deoxy-D-glucitol; PTG, porcine thyroglobulin; RCA, Ricinus comrnunis agglutinin.Enzymes. ,!l-N-Acetyl-D-hexosaminidase (EC 3.2.1.52); acid phosphatase (EC 3.1.3.2); alkaline phosphatase (EC 3.1.3.1); c1-Lfucosidase (EC 3.2.1.51); ,!l-D-galactosidase (EC 3.2.1.23); glucose-6-phosphate dehydrogenase (EC 1.1.1.49); glutamate dehydrogenase (EC 2.4.1.2); hexokinase (EC 2.7.1.1); a-D-mannosidase (EC 3.2.1.24); ,!l-D-mannosidase (EC 3.2.1.25); neuraminidase (EC 3.2.1.18); 6-phosphogluconate dehydrogenase (EC 1 .I .1.43); phosphoglucose isomerase (EC 5.3.1.9); phosphomannose isomerase (EC 5.3.1.8); sul...