Table II.

Solubilized purified organelles exhibit MIPS activity

To assess organelle purity and enrichment, marker enzymes for endoplasmic reticula (antimycin insensitive NADH cytochrome C reductase), mitochondria (cytochrome C oxidase), plastids (nitrite reductase), plasma membranes (vanadate-sensitive Ca²⁺ ATPase), and microbodies (catalase) were assayed using 0.010 mg of protein for each fraction. Contamination between organelles was estimated by comparing the specific activity (S.A.) of the marker enzymes in each fraction with the specific activity of the marker enzyme in its designate organelle.

Fraction ([Protein] = 0.010 mg)	Specific Activity
	Cytochrome C Reductase	Cytochrome C Oxidase	Nitrite Reductase	Ca 2+ ATPase	Catalase (Eref = 3.45 μmol)
	μmol Cyt C red min-1mg-1	μmol Cyt C ox min-1mg-1	nmol NO-2red min-1mg-1	μmol Pi h-1mg-1	μmol H2O2dec min-1
Root
Plastids	0.0296	0.0156	93.310	0.04875	0.0276
Mitochondria	aua	0.4116	30.890	0.01623	0.0690
Microsomes	0.3300	au	au	0.08125	0.0759
Plasma membranes	au	au	au	0.22100	au
Leaf
Chloroplasts	0.0222	0.0254	98.590	0.05177	0.0414
Mitochondria	0.0222	0.2685	22.098	0.04719	0.0483
Plasma membranes	au	0.0137	au	0.25588	0.0449

^aActivity undetectable