Table 2.

Analysis of complex I content and catalytic turnover number in whole tissue homogenates from different mouse tissues, intact mouse brain mitochondria, bovine mitochondria, and SMP

Preparation type	KGDHC FAD content pmol/mg protein	Complex I FMN content pmol/mg protein	NADH:HARa		NADH:Q1a
			Activity μmol × min−1 × mg−1	Turnoverb ×104, min−1	Activity μmol × min−1 × mg−1	Turnoverb ×104, min−1
Brain	17 ± 1	10 ± 1	0.91 ± 0.06	8.96 ± 1.00	0.105 ± 0.004	1.03 ± 0.10
Heart	38 ± 8	50 ± 5	5.39 ± 0.40	10.9 ± 1.29	0.229 ± 0.022	0.46 ± 0.06
Liver	ND	6 ± 1	0.75 ± 0.03	12.1 ± 1.15	0.037 ± 0.002	0.60 ± 0.06
Kidneys	16 ± 8	26 ± 3	1.62 ± 0.03	6.28 ± 0.80	0.125 ± 0.005	0.48 ± 0.06
Muscle	50 ± 3	20 ± 1	1.60 ± 0.10	7.87 ± 0.71	0.076 ± 0.010	0.37 ± 0.05
MB Mtc	65 ± 5	19 ± 1	1.62 ± 0.04	8.68 ± 0.47	0.21 ± 0.02	1.06 ± 0.03
BH Mtc	123 ± 9	51 ± 4	4.46 ± 0.16	8.80 ± 0.74	0.135 ± 0.007	0.27 ± 0.02
BH SMPc	ND	70 ± 6	5.86 ± 0.12	8.43 ± 0.80	0.071 ± 0.005	0.10 ± 0.01

Abbreviation: ND, not detected.

^aActivities were assayed accordingly to the Experimental procedures section at 25 °C in buffer made of 125 mM KCl, 0.02 mM EGTA, 20 mM Hepes–KOH (pH 7.5) and either 1 mM HAR or 40 to 50 μM Q₁. About 100 μM of NADH was added to 2 to 30 or 50 to 400 μg/ml protein for HAR and Q₁ reactions, respectively. Values are given in μmol NADH × min⁻¹ × mg protein⁻¹.

^bEnzyme catalytic turnover (k_cat) was calculated as moles of NADH oxidized per minute per mole of enzyme by dividing activity values in μmol × min⁻¹ × mg protein⁻¹ by enzyme content in micromoles of complex I per milligram of protein.

^cIntact mitochondria from mouse brain (MB Mt), bovine heart (BH Mt), and bovine heart SMP (BH SMP).