APPROACHES TO THE ANALYSIS OF SPECIFIC MEMBRANE TRANSPORT 585 



was found that the weight of the membrane fraction obtained in this way 

 corresponded quite closely to the weight of our small particle lipoprotein 

 fraction, and we discovered, as shown in Table I, that both the small 

 particles and the intact membranes (from which the small particles were 

 evidently derived) contained not only cytochrome pigments, but many 

 enzyme activities [i8, 31]. Similar observations were made soon after by 

 Storck and Wachsman [32] on the membrane fraction of Bacillus mega- 

 terium, and subsequent studies which Dr. Weibull and his collaborators 



TABLE I 



Distribution of Enzymes and Catalytic Carriers in 

 Staphylococcus Aureus 



Enzvnie or catalvtic carrier 



'' Soluble ' 

 fraction 



Plasma membrane or 



lipoprotein particle 



fraction 



Cytochromes (extinction at 425 m/^i) 



Succinic dehydrogenase 



Lactic dehydrogenase 



Malic enzyme 



Malic dehydrogenase 



Formic dehydrogenase 



x-Glycerophosphate dehydrogenase(s) 



CJlucose-6-phosphate dehydrogenase 



Glucose-6-phosphatase 



Acid phosphatase 



have carried out on this organism suggest that in this case, too, the enzyme 

 activities do actuallv belong to the membrane complex and are not carried 

 bv adhering particles [33]. Dr. Moyle and I extended our work to Micro- 

 coccus lysodeikticus with results similar to those obtained with Staphylo- 

 coccus aureus (see [2]). In organisms such as Escherichia coli and Azotohacter 

 riue/audii, where it is very difficult to separate plasma membrane from cell 

 wall material [13, 34], the evidence is perforce less unequivocal, but it 

 seems probable that the so-called insoluble enzymes in these organisms are 

 part of the plasma membrane complex as in the micrococci and Bacillus 

 megateriuui [-^z,, and see 4]. 



the concept of translocation catalysis 



The fact that certain hydrolytic and oxido-reductive enzymes and 

 catalytic carriers, including those of the cytochrome system, are an 

 integral part of the plasma membrane complex of certain bacteria repre- 

 sents the experimental foundation for our conception of the plasma 



