[Enzymatic characteristics of the guanylate cyclase of KB cells: their change as a function of the development of the cultures].
We have localized 71% of the guanylate cyclase activity in the (G X 105,000) supernatent fraction of broken KB cells. The reaction follows Michaelis-Menten kinetics, the apparent Km for GTP is 0,5 mM, as long as GTP is lower than a limited concentration, then activity is inhibited. The ion Mn++ is an absolutely required activator, it does not change enzyme-substrate affinity. The enzyme shows several types of binding sites of Mn++. Guanylate cyclase, studied over a period of development of culture, shows, in KB cells without cell contact, an activity higher than that observed in confluent cells. This is not due to the fact of a change in enzyme-substrate affinity but to a modification of Mn++ influence.
D002448:Cell Adhesion; D002460:Cell Line; D002470:Cell Survival; D006160:Guanosine Triphosphate / Q000378:metabolism; D006162:Guanylate Cyclase / Q000378:metabolism*; D007700:Kinetics; D008345:Manganese / Q000378:metabolism
D008345:Manganese; D006160:Guanosine Triphosphate; D006162:Guanylate Cyclase
Les caractéristiques enzymatiques de la guanylate cyclase des cellules KB, leurs modifications en fonction du développement des cultures