760 Chairman: H. EAGLE 
misquoted here twice. Our interest in this field has been chemical, and our work has been primarily 
on the chemistry of these substances. Anything biological about it has been purely accidental. 
We have encountered compounds of the nature described by Dr. AXELROD and we have encoun- 
tered other classes of compounds, too, such as those described by Dr. HENpDLER. I think there 
are a very large number of substances in the amino acid containing lipid preparations, but 
as to their biological functions, I have no idea. 
As to your question about the lipids; perhaps we have been a little misleading in nomenclature. 
We have always found fatty acids in the same fractions as the amino acids, on hydrolysis. We 
have not proven the structure of any one compound, nor have we ever obtained any one compound 
in sufficient yield to do so. The substances have been called lipids on the basis of solubility and 
fractionation characteristics. 
EacLe: If I understood Dr. MITCHELL correctly, although he has isolated such compounds 
from nature, it is a whole complex of substances rather than a single entity. 
RousER: On the basis of what I have heard up to now, I want to insist that we consider one 
point. None of these so-called lipid—amino acid complexes really seems to be at this time charac- 
terized as lipid-containing amino acids, and I think that this is important. Now, as for lipids and 
bound amino acids associated with each other, this is something different. On the basis of this 
latter definition, I can say that I have isolated such material which I feel is not an artifact. For 
example, we did find amino acids with lipids in rabbit appendix, which is a rapidly growing 
tissue. On the other hand, we found essentially none in brain. However, I am not at all certain 
that these are lipids in the classical sense of the word. 
EaGLeE: Your scepticism can hardly apply to the in vitvo experiments with a defined lipid. 
RousEr: No. I am not talking about Dr. AXxELROD’s experiments. He has clearly demonstrated 
the presence of a fatty acid in his compound. I am talking about the variety of other substances 
that have not so far been characterized as lipid material, but are associated with lipids. 
EaGLeE: You are not prepared to extrapolate from these in-vitvo phenomena to what is isolated 
from tissue? You do not want to extrapolate from Dr. AXELROD’s compound to the compounds 
which are extracted from tissues? 
RouseEr: Oh, no; by no means. 
HENDLER: Dr. RouseEr, I must be missing the point you are making. You say that you have iso- 
lated these complexes and that you are convinced that they are not artifacts of preparation, that 
they actually occur in your tissue, and that they dissolve in organic solvents. Then what I do not 
understand is why you feel that if they do not also contain a long carbon chain that they could 
not be metabolized in non-polar regions of the cell into which they might penetrate. 
RouseEr: That is quite another point. I am not questioning that at all; just the decision that 
these substances are lipids. This is a very distinct and different situation, and I am simply suggest- 
ing that it is causing a great deal of confusion to call them lipids. They might be very important 
metabolic substances and still not be lipids in the practical sense. I think that this is most likely 
the case. 
LorFTFIELD: I do not want to meddle in this little thing, but it seems to me that polyglutamine, 
polyphenylalanine, polylysine, all of the polyamino acids with the exception of polyglycine and 
polyproline, are lipid-soluble as opposed to water-soluble, so that these things which have the 
properties that Dr. RouseEr is talking about could indeed not contain any lipid at all. 
GRIFFITH: There is one fatty acid—amino acid complex of venerable age that ought to be 
mentioned in this connection, viz., benzoic acid, or phenylformic acid, and its combination with 
glycine to form hippuric acid, also phenylacetic with glutamine to form a similar compound. I 
couldn’t help but think of this in connection with the solubility matter, because sodium ben- 
zoate in the blood stream is eliminated very slowly by the kidney whereas hippurate is eliminated 
very rapidly. As far as I can see, the detoxication of benzoic acid that we have known about so 
long is primarily a matter of changing a less to a more diffusible molecule in order to hasten its 
elimination from the body. 
ARONOFF: Dr. HENDLER, did you not use any fatty acids instead of amino acids? 
HENDLER: You mean labeled fatty acids? No. I will have to look into this point. 
L. Mitcer: Dr. HENDLER, did you find any correlation whatsoever between the known protein 
synthetic activity of various tissues, let’s say in the sense in which CaAspERSSON looked at them, 
and the occurrence of these amino acid—lipid complexes? This is an impertinent question on 
several grounds. 
HENDLER: I have not made the studies of CaspERSsON. There are numerous reports now of 
various types of tissue that have been found to contain such compounds, but no systematic effort 
has been made to correlate the existence of these things and the rate of protein synthesis in these 
tissues. 
SEGAL: I would like to ask Dr. AXELROD how his system differs from that described by TAGGART 
in a series of papers in the J. Biol. Chem. in 1953 and 1954, using the kidney to study the forma- 
tion of acylamino acids. 
