Biochemical properties of Na+/K(+)-ATPase in axonal growth cone particles isolated from fetal rat brain.
Axonal growth cones (AGC) isolated from fetal rat brain have an important specific activity of N+/K(+)-ATPase. Kinetic assays of the enzyme in AGC showed that Km values for ATP or K+ are similar to those reported for the adult brain enzyme. For Na+ the affinity (Km) was lower. Vmax for the three substrates was several times lower in AGC as compared to the adult value. We also observed two apparent inhibition constants of Na+/K(+)-ATPase by ouabain, one of low affinity, possibly corresponding to the alpha 1 isoform and another of high affinity which is different to that described for the alpha 2 isoform of the enzyme. These results support an important role for the sodium pump in the maintainance of volume and cationic balance in neuronal differentiating structures. The functional differences observed also suggest that the enzymatic complex of Na+/K(+)-ATPase in AGC is in a transitional state towards the adult configuration.
Mercado
R
R
Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del I.P.N. México, D.F. México.
Hernández
J
J
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D001369:Axons / Q000201:enzymology*; D001921:Brain / Q000196:embryology / Q000201:enzymology* / Q000648:ultrastructure; D005314:Embryonic and Fetal Development / Q000502:physiology; D007700:Kinetics; D010042:Ouabain / Q000037:antagonists & inhibitors; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D012964:Sodium / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D010042:Ouabain; D000255:Adenosine Triphosphate; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium