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ATPase and acid phosphatase activities associated with vacuoles isolated from storage roots of red beet (Beta vulgarisL.)

✍ Scribed by Roger A. Leigh; Robert R. Walker

Publisher: Springer-Verlag
Year: 1980
Tongue: English
Weight: 792 KB
Volume: 150
Category: Article
ISSN: 0032-0935
DOI: 10.1007/bf00390830

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✦ Synopsis

Phosphatase activities were measured in preparations of vacuoles isolated from storage roots of red beet (Beta vulgaris L.). The vacuoles possessed both acid phosphatase and ATPase activities which could be distinguished by their susceptibility to inhibition by low concentrations of ammonium molybdate [(NH4)6Mo7O24·4H2O]. The acid phosphatase was completely inhibited by 100 μM ammonium molybdate but the ATPase was unaffected. The acid phosphatase was a soluble enzyme which hydrolysed a large number of phosphate esters and had a pH optimum of 5.5. In contrast, the ATPase was partially membrane-bound, had a pH optimum of 8.0 and hydrolysed ATP preferentially, although it was also active agianst PPi, GTP and GDP. At pH 8.0 both the ATPase and PPase activities were Mg(2+)-dependent and were further stimulated by KCl. The ATPase and PPase activities at pH 8.0 may be different enzymes. The recovery and purification of the ATPase during vacuole isolation were determined. The results indicate that the Mg(2+)-dependent, KCl-stimulated ATPase activity is not exclusively associated with vacuoles.

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