title: High level of sialate-O-acetyltransferase activity in lymphoblasts of childhood acute lymphoblastic leukaemia (ALL): enzyme characterization and correlation with disease status.
abstract: Previous studies had established an over-expression of 9-O-acetylated sialoglycoproteins (Neu5,9Ac(2)-GPs) on lymphoblasts of childhood acute lymphoblastic leukaemia (ALL). Here, we report the discovery and characterization of sialate-O-acetyltransferase enzyme in ALL-cell lines and lymphoblasts from bone marrow of children diagnosed with B- and T-ALL. We observed a positive correlation between the enhanced sialate-O-acetyltransferase activity and the enhanced expression of Neu5,9Ac(2)-GPs in these lymphoblasts. Sialate-O-acetyltransferase activity in cell lysates or microsomal fractions of lymphoblasts of patients was always higher than that in healthy donors reaching up to 22-fold in microsomes. Additionally, the V (max) of this enzymatic reaction with AcCoA was over threefold higher in microsomal fractions of lymphoblasts. The enzyme bound to the microsomal fractions showed high activity with CMP-N-acetylneuraminic acid, ganglioside GD3 and endogenous sialic acid as substrates. N-acetyl-7-O-acetylneuraminic acid was the main reaction product, as detected by radio-thin-layer chromatography and fluorimetrically coupled radio-high-performance liquid chromatography. CMP and coenzyme A inhibited the microsomal enzyme. Sialate-O-acetyltransferase activity increased at the diagnosis of leukaemia, decreased with clinical remission and sharply increased again in relapsed patients as determined by radiometric-assay. A newly-developed non-radioactive ELISA can quickly detect sialate-O-acetyltransferase, and thus, may become a suitable tool for ALL-monitoring in larger scale. This is the first report on sialate-O-acetyltransferase in ALL being one of the few descriptions of an enzyme of this type in human.
authors.affiliation: Infectious Diseases and Immunology Division, Indian Institute of Chemical Biology, 4 Raja S.C. Mullick Road, Jadavpur, Kolkata 700 032, India.
authors.forename: Chandan
authors.initials: C
authors.lastname: Mandal
authors.forename: G Vinayaga
authors.initials: GV
authors.lastname: Srinivasan
authors.forename: Suchandra
authors.initials: S
authors.lastname: Chowdhury
authors.forename: Sarmila
authors.initials: S
authors.lastname: Chandra
authors.forename: Chhabinath
authors.initials: C
authors.lastname: Mandal
authors.forename: Roland
authors.initials: R
authors.lastname: Schauer
authors.forename: Chitra
authors.initials: C
authors.lastname: Mandal
mesh_terms: D000105:Acetyl Coenzyme A / Q000378:metabolism; D000123:Acetyltransferases / Q000378:metabolism*; D000293:Adolescent; D001853:Bone Marrow / Q000201:enzymology* / Q000473:pathology; D045744:Cell Line, Tumor; D002648:Child; D002675:Child, Preschool; D003568:Cytidine Monophosphate / Q000378:metabolism; D006801:Humans; D007223:Infant; D008297:Male; D008861:Microsomes / Q000201:enzymology* / Q000473:pathology; D019158:N-Acetylneuraminic Acid / Q000378:metabolism; D009363:Neoplasm Proteins / Q000378:metabolism*; D015452:Precursor B-Cell Lymphoblastic Leukemia-Lymphoma / Q000201:enzymology* / Q000473:pathology; D054218:Precursor T-Cell Lymphoblastic Leukemia-Lymphoma / Q000201:enzymology* / Q000473:pathology
chemical_list: D009363:Neoplasm Proteins; D000105:Acetyl Coenzyme A; D000123:Acetyltransferases; C018766:N-acylneuraminate-9(7)-O-acetyltransferase; D003568:Cytidine Monophosphate; D019158:N-Acetylneuraminic Acid