Life Science* zyxwvutsrqponmlkjihgfedc Vol. 62, zyxwvutsrqponmlkjihgfe No. 25, pp. zyxwvutsrqponml 22%2266,199s cqyright 0 1998 Ebcvier scitace Inc. Rintod in the USA. All tipjlta twotvod ELSEVIER PII SOO24-3205(98)00206-9 orad-=/ s19.00 t .oo BEHAVIOUR OF HUMAN LYMPHGCYTIC ISOENZYMES OF 5’NUCLEOTIDASE F Rosi*, Al3 Agostinho*, F Carlucci*, L Zanoni*, B Porcelli*, E Marinello*, P GalieniO and A Tabucchi* *Institute of Biochemistry and Enzymology, University of Siena, Siena, Italy Wepartment of Haematology, Azienda Ospedaliera Senese, Siena, Italy (Received in final form March 25.1998) zyxwvutsrqponmlkjihgfedcbaZYXWV Summary The behaviour of 5’-nucleotidase isoenzymes (ecto-5’-nucleotidase, e-Ns and c- N-II soluble 5’-nucleotidases) was studied in lymphocytes from patients with B- cell chronic lymphocytic leukemia. A strong reduction in ecto- and soluble activities was observed, although the pattern of the three 5’nucleotidases did not always strictly overlap. A significant decrease (p<O.OS) in ecto-5’-nucleotidase, e- Ns and c-N-11 was found in B and T populations (B lymphocytes: 1.13, 0.88 and 1.26 mnol/h/106 cells versus 95.%, 9.64 and 13.73 nmol/h/106 cells in controls; T lymphocytes: 1.31, 0.23 and 0.06 nmol/h/106 cells versus 9.25, 1.31 and 2.10 nmol/h/106 cells in healthy subjects). The percentage of ecto-5’-nucleotidase- positive cells (CD73+) was reduced in leukemia patients, indicating a lower number of active molecules on the cell surface. The results of RT-PCR analysis showed that the ecto-5’-nucleotidase mRNA of leukemia patients was not defective. ZCey Wwrls: e&d * -nueleotidase, B-cell chronic lymphocytic leukemia, lymphocytes, HPLC Ecto-5’-nucleotidase (ecto-5’-NT: E.C. 3.1.3.5) is a very well known enzyme which catalyzes the dephosphorylation of puke and pyrimidine nucleoside 5’-monophosphates to the corresponding nucleosides, the preferred substrate being AMP. The enzyme is a dimer of two identical 70 KDa subunits bound by a glycosyl phosphatidyl inositol linkage to the external face of the plasma membrane of various cells, including subsets of human lymphocytes; it has been extensively studied in rat liver and heart, and in murine and human placenta (l-5). The gene coding for human e&o-5’-nucleotidase is located on chromosome 6 (6). The cDNA corresponding to the human placental e&-enzyme has been sequenced (7, 8). In human lymphocytes two soluble 5’-nucleotidases are present also. The first form reveals a preference for AMP as substrate and is known as e-Ns; the second form, called c-N-11,has a preference for IMP as substrate and controls intracellular levels of nucleoside 5’- monophosphates. Address for correspondence: Prof. Enrico Marinello, Istituto di Biochimica e di Enzimologia, Universita di Sierra, Pian dei Mantellini, 44, 53100 - Sierra, Tel: +39-577-298026, FAX +39-577- 29805