Table III.

PSD activity in total membranes and purified mitochondria of wild-type Arabidopsis and a knockup mutant

PSD activity was measured in a total (80,000g) membrane pellet prepared from leaf extracts and in root mitochondria purified by Percoll density gradient centrifugation. The roots were cultured in Murashige and Skoog medium. Ptd[1-¹⁴C]Ser and NBD-Ptd-[1′-¹⁴C]Ser were used as substrates. Data are means of three replicates ± se.

Substrate	Total Membranes		Purified Mitochondria
	Wild Type	Mutant	Wild Type	Mutant
		nmol min-1 mg-1
Ptd[1-14C]Ser	0.412 ± 0.087	0.481 ± 0.072	0.034 ± 0.048	0.295 ± 0.021
NBD-Ptd-[1′-14C]Ser	0.112 ± 0.016	0.154 ± 0.028	<0.015	0.134 ± 0.025