Table 2.

Effect of tenuazonic acid (TeA) on K _m and V _max of the Spinacia oleracea plasma membrane (PM) H⁺‐ATPase.

Tenuazonic acid (μM)	K m (mM ATP)	V max (nmol Pi mg−1 min−1)
Control	1.15 (0.59–1.71)	332.4 (262.9–401.8)
1.0	2.56 (0.74–4.38)	219.3 (132.5–306.1)
2.5	10.96 (0.0–37.0)	83.8 (−76.6–244.2)

ATP hydrolysis of S. oleracea PM fractions was measured at different ATP concentrations in response to various TeA doses, and enzyme kinetic constants, K _m and V _max, were determined from nonlinear regression of the Michaelis–Menten equation. Values are means ± SEM of four technical replicates of two independent PM fractions (n = 8).