Table II.

Substrate specificity of ACOX and ACAD activities in peroxisomes and high-density mitochondria from carbohydrate-starved maize root tips

Substrate	ACOX Activity in Peroxisomes	ACAD Activity in High-Density Mitochondria
50 μm	nmol min−1 mg−1
Butyryl-CoA	5.7  ± 0.5	2.5  ± 0.4
Isobutyryl-CoA	0.60  ± 0.05	2.3  ± 0.6
Isovaleryl-CoA	NDa	1.2  ± 0.3
Hexanoyl-CoA	8.0  ± 0.7	4  ± 1
Octanoyl-CoA	7.1  ± 0.3	4  ± 2
Palmitoyl-CoA	3.5  ± 0.3	5  ± 1

ACOX and ACAD activities were measured as described in Methods. Partially purified peroxisomes and purified high-density mitochondria were isolated from 48-h carbohydrate-starved maize root tips, as previously described (Couée et al., 1992; Dieuaide et al., 1993). Results are the means ± se of at least three experiments.

^aND, Not detected.