Table II.

Identification of products synthesized using specific inhibitors of tonoplast proton pumps

Additions	Products Synthesized
	Coleoptiles		Seeds
	ATP	PPi	ATP	PPi
	nmol mg−1 30 min−1
ATP	3.5  ± 0.3 (n = 6)	8.2  ± 2.5 (n = 6)	1.3  ± 0.5 (n = 6)	2.3  ± 1.1 (n = 6)
ATP + KF	3.0  ± 1.6 (n = 3)	0	1.6  ± 1.1 (n = 3)	0
PPi	9.6  ± 0.9 (n = 6)	7.1  ± 2.8 (n = 6)	8.0  ± 1.2 (n = 6)	12.8  ± 2.3 (n = 6)
PPi + Bafilomycin A1	0	12.5  ± 1.6 (n = 3)	0	11.3  ± 2.4 (n = 3)

The enzymatic identification of products synthesized (Fig. 4) is compared with experiments of phosphate exchange performed either in the presence of 10 nm Bafilomicin A₁, a specific inhibitor of V-ATPase, or with vesicles preincubated with 10 mm KF, an inhibitor of H⁺-PPase. The specific activity of products was calculated from radioactivity remaining after phosphomolybdate extraction. The total ³²Pi incorporated in the presence of each substrate and in the absence of inhibitors (data not shown) are in the range presented as “Control” in Figure 4. The reaction medium contained 50 mm MOPS-Tris, pH 7.0, 5 mm MgCl₂, 5 mm ³²Pi, 100 mm KCl, 0.1 mm ADP, and either 1 mm ATP or 1 mm PPi. The reaction was started by the addition of 0.05 mg/mL protein. Values represent the means ± se of n independent experiments. PPi values were corrected for two Pi incorporated into each PPi.