Characterization of gamma-glutamyltranspeptidase from human pancreatic cancer

To elucidate the specific changes of pancreatic gamma-glutamyl-transpeptidase (gamma-GTP) associated with malignant transformation, some properties of gamma-GTP purified from pancreatic cancer were compared with those of gamma-GTPs from normal pancreas and other tissues. Four of five pancreatic cancer gamma-GTPs showed distinctly slower electrophoretic mobility than normal pancreatic enzymes. Isoelectric points of pancreatic cancer gamma-GTPs varied in each case, but they were all higher than those of normal pancreatic enzymes. This difference in isoelectric points of gamma-GTPs between cancerous tissue and normal tissue was reduced by neuraminidase treatment. Lectin affinity chromatography revealed two of five pancreatic cancer gamma-GTPs with a greater affinity to concanavalin A (Con A) than normal pancreas gamma-GTPs. Four of five pancreatic cancer gamma-GTPs had a greater affinity to Lens culinaris agglutinin (LCA) than normal pancreas gamma-GTPs. Normal pancreas gamma-GTPs had little affinity to Phaseolus vulgaris erythroagglutinating (E-PHA), but two of five pancreatic cancer gamma-GTPs had an apparent affinity to E-PHA and one of them had a slight affinity to E-PHA. These results indicate that the transformational changes of pancreatic cancer gamma-GTP are mainly induced in the sugar chains of the enzyme molecule, resulting in lower content of sialic acid and higher content of fucose and bisecting GlcNAc residue (the beta-N-acetylglucosamine residue linked at the C-4 of the beta-mannosyl residue of the trimannosyl core of the asparagine-linked sugar chain) as compared with the normal pancreatic enzyme.