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Glycoconj J. 2009 Jan;26(1):57-73. doi: 10.1007/s10719-008-9163-3. Epub 2008 Aug 3.

High level of sialate-O-acetyltransferase activity in lymphoblasts of childhood acute lymphoblastic leukaemia (ALL): enzyme characterization and correlation with disease status.

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1
Infectious Diseases and Immunology Division, Indian Institute of Chemical Biology, 4 Raja S.C. Mullick Road, Jadavpur, Kolkata 700 032, India.

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.

PMID:
18677580
DOI:
10.1007/s10719-008-9163-3
[Indexed for MEDLINE]

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