PT  - JOURNAL ARTICLE
AU  - A. Y. DIVEKAR
AU  - M. T. HAKALA
TI  - Adenosine Kinase of Sarcoma 180 Cells
DP  - 1971 Nov 01
TA  - Molecular Pharmacology
PG  - 663--673
VI  - 7
IP  - 6
4099  - http://molpharm.aspetjournals.org/content/7/6/663.short
4100  - http://molpharm.aspetjournals.org/content/7/6/663.full
SO  - Mol Pharmacol1971 Nov 01; 7
AB  - Adenosine kinase (ATP:adenosine 5'-phosphotransferase, EC 2.7.1.20) was partially purified by DEAE-cellulose column chromatography from Sarcoma 180 cells grown in vitro. This enzyme preparation, which was free of adenosine deaminase (adenosine aminohydrolase, EC 3.5.4.4) but contained adenylate kinase (ATP:AMP phosphotransferase, EC 2.7.4.3), was studied with respect to its kinetic properties and specificity for substrates and inhibitors. At pH 7.0 and 35° the Km for adenosine was 0.5 µM and the Vmax was 63 mµmoles/mg of protein per minute. Strong substrate inhibition was observed at adenosine concentrations greater than 4 µM, 50% inhibition occurring at about 100 µM. The reaction required ATP (Km = 200 µM) and Mg++. The optimal Mg++ concentrations were 0.1 and 0.25 mM at 0.5 and 2.5 mM ATP, respectively. Concentrations of Mg++ higher than these were inhibitory, and Mn++ substituted poorly for Mg++. Most of the N6-substituted adenosine analogues which were substrates of adenosine kinase inhibited the growth of S-180 cells in vitro. Among these were two compounds which are also known to be potent cytokinins in plant systems, namely, N6-furfuryl- and N6-(Δ2-isopentenyl)adenosine. The 5'-monophosphate of the latter compound was not phosphorylated further by adenylate kinase. The N6-substituted adenosines which were poorly or not at all phosphorylated by adenosine kinase were also poor inhibitors of S-180 cells in vitro. Several of these were potent inhibitors of the kinase, such as N6-phenyladenosine, which had a Ki value of 0.6 µM. ACKNOWLEDGMENT The authors wish to express their appreciation to Miss Dorris Sugg for her excellent assistance in these studies.