. 2009 Jan 30;60(3):993–1008. doi: 10.1093/jxb/ern343

Table 1.

OASS/CAS activities and kinetic parameters of OsCAS in rice, OsCAS–YFP in transgenic Arabidopsis, and OsCAS–YFP yeast transformant

Organisms	OASS-specific activity (μmol Cys min⁻¹ mg⁻¹ protein)	CAS-specific activity (μmol H₂S min⁻¹ mg⁻¹ protein)	Activity ratio of CAS/OASS	K_m for CAS reaction (mM)		Inhibition on CAS activity
Organisms	OASS-specific activity (μmol Cys min⁻¹ mg⁻¹ protein)	CAS-specific activity (μmol H₂S min⁻¹ mg⁻¹ protein)	Activity ratio of CAS/OASS	Cys	KCN	Cyanide IC₅₀ (mM)^a
Rice	N.D.^b	13.3^c	/	0.84	0.27	/
Arabidopsis	0.92±0.06	181±13.89	197	1.07±0.20	0.67±0.15	20
Yeast	1.84±0.77	111.3±5.11	60.5	0.91±0.11	0.31±0.01	40

K_m values were calculated by linear regression of double-reciprocal plots. Measurements of enzyme activities and determinations of K_m values were repeated at least three times.

The concentration of cyanide required for 50% inhibition of CAS activity. IC₅₀ was determined as 20 mM for spinach CAS previously by Warrilow and Hawkesford (2000).

N.D., Not detected.

CAS specific activity was determined on partially purified fraction (750-fold) from etiolated rice seedling extract.