High expression of udp-n-acetylglucosamine: β-d mannoside β-1, 4-n-acetylglucosaminyltransferase III (GnT-III) in chronic myelogenous leukemia in blast crisis

The activity and mRNA expression of UDP-N-acetylglucosamine: β-D mannoside β-1,41-N-acetylglucosaminyl transferase III (GnT-III: EC 2.41.1.144) were investigated in hematological malignancies. GnT-III activity was eleuated in patients with chronic myelogenous leukemia (CML) in blast crisis and patients with multiple myeloma (MM), as compared to normal healthy subjects and patients with other hematological malignancies including CML in chronic phase. The GnT-III transcript was the mme size in leukemic cells from various hematological diseases and cell lines, while expression of the transcript was not found to correlate significants with enzyme activity, implying that post-translational modification might regulate the activity of GnT-III. Southern-blot analysis showed no significant uariation in the structure and position of the GnT-III genome, indicating that the gene is present as a single copy without isoforms. Furthermore, analyses by immunoprecipitation and Western blot revealed that high GnT-III activity in KU812 cell, a CML cell line, resulted in an increase in E 4 -PHA binding to CD415, a major surface glycoprotein of the leukocyte, indicating that more bisecting GlcNAc was added to CD415 catalyzed by elevated GnT-III