144 S. S. COHEN 



Chantrenne (1956a) has observed the incorporation of adenine and uracil 

 in yeast nucleic acids during the formation of catalase and some other 

 enzymes which are induced by oxygen in a respiration-deficient, anaerobicaEy 

 grown yeast. ^ In this system the enzymes produced do not contribute to cell 

 growth. In additional experiments, it is reported (Chantrenne, 1956b) that 

 the increased incorporation of adenine caused by the presence of the inducer 

 is observed even when enzyme formation is blocked by jo-fluorphenylalanine, 

 suggesting that the tooling of the enzyme-forming site may be separated 

 from actual enzyme production. 



Finally, several reports have appeared indicating that polynucleotide 

 fractions from induced cells may be added to uninduced cells in the absence 

 of inducer and thereby stimulate enzyme production. Reiner and Goodman 

 (1955) have reported that lactate-grown E. coli will produce gluconokinase 

 if incubated with ATP and polynucleotide prepared from gluconate-grown 

 cells. RNAase does not destroy the activity of the polynucleotide but renders 

 it dialyzable. Kramer and Straub (1956) have observed that an RNAase- 

 sensitive nucleic acid preparation from penicillin-induced B. cereus was 

 capable of stimulating penicillinase production in uninduced organisms. In 

 the latter case of the addition of the specific nucleic acid to the iminduced 

 bacterium, enzyme production started at a high rate and decreased after 

 20 mmutes, suggesting the possible degradation of the template during 

 enzyme formation. 



4. On Induction 



Several hy]3otlieses have appeared on the nature of inducer action which 

 relate the biosynthesis of the enzyme to the presence or activity of the 

 enzyme. One of these supposes that an inducer is a substrate of the enzyme; 

 another, that enzyme production is shifted toward synthesis by complexing 

 with the enzyme and removing it from the synthetic system. The first of these 

 hypotheses has been excluded by demonstrations that induction can occur 

 under conditions in which the inducer is not metabolized. For example, 

 thiomethyl-jS-D-galactoside and melibiose, inducers of ^-galactosidase in E. 

 coli strain ML, are not cleaved by the enzyme (Monod et al., 1951). In the 

 same study it was shown that a substance which complexes with the enzyme 

 is not an inducer, thereby excluding the second so-called "mass action" 

 hypothesis, at least in its simplest form. Phenyl-^-D-thiogalactoside has such 



^ The effect of oxygen in stimulating cytochrome synthesis in anaerobically grown 

 yeast is quite obscure at present. The synthesis of many other enzymes, e.g., enzymes of 

 the tricarboxylic acid cycle, is also stimulated, and unless one conceives of an elaboration 

 of all of these enzymes occurring by some special type of reverse sequential induction, it 

 is difficult to classify this jiattern of induced enzyme biosynthesis with the others dis- 

 cussed above. 



