Table 5.

Enzyme activities of AtSPDS1 wild type and mutants.

Enzyme	Exchanges	SPDS activity	PMT activity
		vmax [pkat mg−1]	vmax [pkat mg−1]	Km putrescine [μM] Km SAM [μM]	kcat [1 s−1]
AtSPDS1 wild type	–	20,722 ± 351.1	–	220 ± 18.44	0.722
				18 ± 1.23 (dcSAM)
AtSPDS1 mutant	D131I	29 ± 0.74	119 ± 2.74	56 ± 4.45	4.48 × 10−3
				28 ± 0.77
	D131I,	6 ± 0.33	100 ± 0.75	126 ± 9.22	3.80 × 10−3
	Q107T			38 ± 1.43
	D131I,	14 ± 1.28	250 ± 2.18	85 ± 5.24	9.51 × 10−3
	V134T			65 ± 2.54
	D131I,	4 ± 0.58	2155 ± 17.55	32 ± 1.88	0.081
	Q107T,			12 ± 0.60
	V134T
	D131I,	<d.l.	144 ± 1.61	100 ± 7.67	5.47 × 10−3
	Q107T,			50 ± 2.65
	V134T,
	L98H

<d.l., below detection limit; n.d., not determined; n = 3–4 ± standard error.