188 S. Spiegelman 



protoplasts of B. megaterium. We may note, however, that, 

 in addition to inducer, a supply of amino acids, hexose- 

 diphosphate, and aerobiosis were found to be essential. As 

 with other synthetic functions, the properties of enzyme 

 formation in protoplasts and intact cells were remarkably 

 similar, providing the comparisons were carried out under 

 hypertonic conditions. 



The interest in the protoplast as a possible tool in the further 

 analysis of enzyme synthesis stems essentially from the 

 possibility that it would be more amenable to specific enzyma- 

 tic resolution than the intact cell from which it is derived. 

 Fortunately, this possibility is potentially attainable, for it is 

 when one examines responses to various enzymes that striking 

 differences between protoplasts and cells begin to emerge. 

 This, for example, is clearly exhibited in Table I in the case 



Table I 



Effect of Trypsin and Lipase on Enzyme Formation in 



Cells and Protoplasts 



Cells or protoplasts were suspended in inducer-free induction medium 

 (O-SM-KgHPOi at pH 7-8; 2 % amino acids, 0-6% hexosediphosphate) and 

 incubated with the indicated enzyme for 1 hour, subsequent to which inducer 

 (0 • 06 M lactose, final concentration) was added. The enzyme formed in the next 

 two hours is recorded in terms of the m[j,M of o-nitrophenyl-^-D-galactoside 

 hydrolysed per ml. per minute. 



of the response to lipase and trypsin. Intact cells are com- 

 pletely insensitive to the enzymes whereas the synthetic 

 ability of protoplasts is completely abolished. 



These results illustrate a point worthy of the attention of 

 those concerned with performing and interpreting experiments 

 with subcellular fractions. One might perhaps be led to 

 conjecture that a lipid is a key component of the enzyme- 

 forming mechanism, based simply on the observation re- 

 corded with lipase. However, the fact is that the loss of 

 enzyme-synthesizing ability is a simple consequence of the 



