Table 2.

Comparison of Ca²⁺-Dependent TGase Activity with KGDHC, GDH, mitAspAT, and LDH Activities in Homogenate (H) and Highly Purified Nonsynaptosomal Mitochondria (P6) Obtained from Mouse Brain^a

	total activityb		specific activitiesc		ratio of specific activities
enzyme	H	P6	H	P6	P6/H	recovery in P6 relative to H (%)
KGDHC	8.8 ± 1.4	0.79 ± 0.24	10.4 ± 0.6	80 ± 26d	7.6 ± 2.2	8.8 ± 2.3
GDH	9.6 ± 2.4	0.39 ± 0.05	11.1 ± 1.8	38 ± 3d	3.5 ± 0.3	4.2 ± 0.8
mitAspATe	70 ± 20	3.69 ± 1.10	79 ± 15	356 ± 91d	4.4 ± 0.5	4.5 ± 0.7
LDH	303 ± 74	≤0.15	353 ± 74	≤0.17d	≤0.05	≤0.05
TGase	25 ± 5	0.047 ± 0.007	33 ± 13	4.7 ± 0.6d	0.18 ± 0.05	0.21 ± 0.06

^aThe H and nonsynaptosomal mitochondria (P6) were prepared from the brains of 6-month-old B6/CBA51/J mice. The data are averages from three separate preparations. In each preparation, activities were measured in triplicate (except TGase, where activities were determined in duplicate). Each preparation was from 15 forebrains (∼5 g of wet weight).

^bUnits are μmol/min, except TGase, where activity is expressed as nmol/h.

^cUnits are nmol min⁻¹ (mg of protein)⁻¹, except TGase, where specific activity is expressed as pmol h⁻¹ (mg of protein)⁻¹.

^dSignificantly different from the H values with p = 0.05 by the Mann–Whitney U test.

^eBrain homogenates contain both cytAspAT and mitAspAT. The two activities were distinguished by their relative susceptibility to heat treatment (see the Experimental Procedures). Analysis for cytosolic and mitochondrial isoforms (see the Experimental Procedures) showed that 50 ± 2% of the total AspAT activity in the homogenate was due to mitAspAT.