that the polyhedral organelles constitute about 10% of the total cell protein, which is

consistent with previous electron microscopy, which showed that these structures occupy

a significant portion of the cytoplasm of S. enterica grown under the conditions used for

organelle purification (Bobik et al. 1999, Havemann et al. 2002).

Other Activities of the Polyhedral Organelles

      In addition to measuring diol dehydratase activity of the polyhedral organelles,

propionaldehyde dehydrogenase and adenosyltransferase activities were also measured.

No adenosyltransferase activity was detected in 50ug of polyhedral organelles however,

the specific activity of propionaldehyde dehydrogenase was followed throughout the

purification and the results are summarized in Table 4-2. Unlike diol


Table 4-2. Propionaldehyde dehydrogenase activity during organelle purification
                Protein       Activity     Specific                   Fold 
Sample          (mg)          (U)a         activity      Yield (%)    purification
                                           (U/mg)
Crude extract   515           152          0.295         100           1
Detergent/salts 337.9         205.2        0.607         135          2.1
treatment
12,000 x g      338.8         169          0.50          111          1.7
super
48,000 x g         5.0        9.6           1.92         6.3          6.5
pellet
12,000 x g         4.3        8.6          2             5.7          6.8
super
Sucrose            0.3        1.2          4             0.8          13.6
density
gradient
aActivities were calculated from the initial rate and one unit activity was defined as the amount of enzyme that catalyzes the formation of 1 [tmol of NADH per min per mg.

dehydratase activity, which remained unchanged after detergent treatment,

propionaldehyde dehydrogenase activity increased nearly three-fold. By itself, this result

would suggest that cell debris and/or lipid membranes may be inhibiting propionaldehyde