title: Effect of concanavalin A on the kinetics of ecto-5'-adenosine monophosphatase (5'-adenosine monophosphate phosphohydrolase) in the outer surface of intact neural cells in culture.
abstract: Oncogenic cultured rat C6 astroblastoma cells display strikingly high ecto-5'-adenosine monophosphatase (ecto-5'-AMPase) activity, 4.23 +/- 20 mumol of Pi liberated by intact cells from 3 mM extracellular 5'-AMP (mg of protein-1 h-1, as compared with 0.15 +/- 0.01 for nononcogenic cultured hamster astroblasts. A further rise in C6 cell ecto-5'-AMPase activity occurs with increase in cell density during growth. Less than 2 pg of the lectin, concanavalin A (Con A), bound per cell reversibly inhibits most of the cellular ecto-5'-AMPase activity. Inhibition by Con A binding is independent of cellular temperature. Con A binding suppresses phosphohydrolase activity of a pK=7.4 functional group on the cell surface. A direct proportionality is observed between quantity of Con A bound to the cell surface and simultaneous relative decreases both in Michaelis constant and maximum velocity of ecto-5'-AMPase in the intact cell. The findings suggest that a major consequence of the specific high affinity binding of Con A to the C6 cell surface is the inactivation of the enzyme--substrate complex of ecto-5'-AMPase.
mesh_terms: D000249:Adenosine Monophosphate; D000818:Animals; D001254:Astrocytoma / Q000201:enzymology; D002460:Cell Line; D002462:Cell Membrane / Q000201:enzymology; D003208:Concanavalin A / Q000494:pharmacology*; D006224:Cricetinae; D007700:Kinetics; D009374:Neoplasms, Experimental / Q000201:enzymology; D009708:Nucleotidases / Q000378:metabolism*; D051381:Rats
chemical_list: D003208:Concanavalin A; D000249:Adenosine Monophosphate; C019598:5'-adenosine monophosphate phosphohydrolase; D009708:Nucleotidases