Comparison of plasma membrane H+-ATPase activity in vesicles obtained from dry and hydrated maize embryos.
ATP hydrolysis from H+-ATPase of plasma membrane was measured in vesicles from maize embryos imbibed at times between 0 and 5 h. The activity had a maximum at 2 h of imbibition. In order to detect whether the enzyme had the same characteristics through the first 5 h of imbibition, vanadate and lysophophatydilcholine sensitivities, as well as trypsin, pH and temperature effects on the activity of the H+-ATPase from plasma membrane vesicles isolated from embryos imbibed at 0 or 5 h were studied. The results indicate that the activity expressed at 0 h is very different from the activity at 5 h. The activity from embryos imbibed for 5 h was less sensitive to vanadate, trypsin and lysophosphatidylcholine, more sensitive to denaturing temperatures and with a broader pH dependence, as compared to the activity from embryos that were not imbibed. When vanadate-sensitive ATPase activity was purified by anion exchange chromatography, the peaks obtained from the 0 and 5 h imbibed embryos were different and non-overlapping. These data could be interpreted in terms of different enzyme structures from dry and imbibed embryos due to either different primary structures or covalent modifications, or differences in membrane vicinities.
Sánchez-Nieto
S
S
Departamento de Bioquímica, Facultad de Química, Conjunto E. UNAM, Cd. Universitaria, Coyoacán, 04510 Mexico DF, Mexico.
de Gómez-Puyou
M T
MT
Rodríguez-Sotres
R
R
Carballo
A
A
Gavilanes-Ruíz
M
M
D002462:Cell Membrane / Q000201:enzymology; D018525:Germination; D006863:Hydrogen-Ion Concentration; D006180:Proton-Translocating ATPases / Q000302:isolation & purification / Q000378:metabolism; D012639:Seeds / Q000201:enzymology; D013696:Temperature; D014357:Trypsin; D014638:Vanadates; D014867:Water; D003313:Zea mays / Q000196:embryology* / Q000201:enzymology
D014867:Water; D014638:Vanadates; D014357:Trypsin; D006180:Proton-Translocating ATPases