TABLE 3.

PDHC activity and protein spot 90 levels in cell extracts from cultures grown at different a_w values

awa	Protein 90 levelb	PDHC activityc
0.996	1.67	1.6 ± 0.3
0.97	NDd	3.3 ± 0.7
0.95	6.23	4.9 ± 1.0
0.94	ND	6.8 ± 1.0
0.89	9.17	ND

^aCells were grown to the exponential phase in TSB medium containing various amounts of added NaCl to bring the a_w of the medium to the indicated value.

^bThe relative level of protein spot 90 on representative 2D PA gels was determined by scanning densitometry and is expressed in arbitrary volume units. Each gel was loaded with 150 μg of total membrane-associated protein.

^cThe measured ¹⁴CO₂-generating activity (nanomoles of CO₂ per milligram of protein per minute) was found to be dependent on the presence of NAD in the assay buffer (data not shown), eliminating the possibility that other pyruvate-metabolizing enzymes (such as pyruvate decarboxylase) were responsible for all or part of the measured activity and indicating that the activity was carried out by an intact PDHC (since the NAD-consuming reaction is performed by PdhD). Values shown are averages obtained from duplicate measurements from at least two replicate experiments ± standard deviations.

^dND, not determined.