LIPO—AMINO ACID COMPOUNDS 743 
time-honored conditions of ZAMECNIK AND KELLER? we had no difficulty in detecting 
incorporation of radioactive phenylalanine into protein, and in finding, at the same 
time that lipid material was also labeled*, 4 (Fig. 1). The behavior of whole super- 
natants of rat spleen and pancreas resembled that of liver. Here it must be emphasized 
that the lipoidal material in question was that which was extracted from the 
precipitate obtained with trichloroacetic acid. Such a precipitate would consist not 
only of protein and nucleic acid, but also would contain the microsomes as well. It 
should be noted that incorporation into lipid continued long after the level of activity 
in the protein became constant. In another experiment, when the microsomes and 
TABLE I* 
EFFECT OF VARIOUS TREATMENTS ON [!C|PHENYLALANINE INCORPORATION 
INTO PROTEIN AND LIPID 
Whole supernatant solutions (and the controls) were incubated for 5 min at 37° with the enzymes 
specified after which the other components of the incubation mixture were added. 
Total incubation time: 2 h. 

Relative specific activity in 
Treatment = ; =a 

Protein Lipid 

None 100** LOOn™ 
ATP and 3-phosphoglyceric acid omitted 21 115 
NaF (1o-? 7; ATP and 3-phosphoglyceric acid omitted) 33 99 
p-Chloromercuribenzoate (10-% J) 15 86 
Chloramphenicol (6.2 - to-3 W) Jo 84 
RNAase (0.1 mg/ml) 42 107 
Crotoxin (20 ug/ml) 13 393 


* By courtesy of the J. Biol. Chem. 
** Actual specific activity (counts/min/mg) of protein and of lipid separately set equal to 1oo. 
The values in one column cannot be compared directly to those in the other. 
the microsome-free supernatant were examined separately, radioactivity was found 
in the protein and lipid material in both fractions. Incubation of the supernatant 
fraction alone gave even better incorporation into lipid than when microsomes were 
present. 
In the course of these incubations 3-p-phosphoglycerate-ATP was used in con- 
junction with the endogenous glycolytic system as a source of energy. Omission of 
these chemicals resulted in a substantial reduction of incorporation into protein, but 
incorporation into lipid was not effected (Table I). Similarly, as expected, the pre- 
sence of ribonuclease reduced incorporation into protein but had no effect on the 
radioactivity found in the lipid. Crotoxin, which HENDLER! found depressed the 
overall incorporation of labeled amino acid into hen-oviduct mince, severely depressed 
the incorporation into protein but caused a marked increase in the amount of label 
found in the lipid (Table 1). 
In our earlier work we found a preferential diminution of labeling in protein to be 
caused by lipoxidase but we have not been able to repeat this. 
The relative degree of incorporation of several other amino acids into the protein 
References p. 749 
