INVITED DISCUSSION 
LOMBRICINE AND SERINE ETHANOLAMINE PHOSPHODIESTER 
A. H. ENNOR anp H. ROSENBERG 
Department of Biochemistry, John Curtin School of Medical Research, 
Australian National University, Canberra (Australia) 
Both serine ethanolamine phosphodiester (SEP, I) and lombricine (II) have been dis- 
covered only recently and are compounds of more than usual interest. SEP is now 
known to exist in nature in both its isomeric forms; these have different and peculiar 
distributions and demonstrably different functions, although the importance and 
function of the L-isomer is as yet unknown. 
L-SEP owes its recognition to the work of RoBERTS AND Lowe!, who detected it as 
a ninhydrin-positive spot on a paper chromatogram of an alcoholic extract of river 
turtle (Pseudemys elegans) muscle. Sufficient material was isolated from paper 
chromatograms to permit acid degradative studies as a result of which serine, serine 
phosphate, ethanolamine, ethanolamine phosphate and inorganic phosphate were 
detected as products. RopERTS AND Lowe! identified the serine moiety as the L- 
isomer and suggested the structure: 
O 
|| 
H,N-CH,:CH,-O-P-O-CH,-CH-COOH 
| 
OH NH, 
I 
which was subsequently confirmed by synthesis?. Further investigations indicated 
that L-SEP was present also in snake and alligator muscle’. Intracardiac injection 
of turtles with ®2P, led to labelling of ethanolamine phosphate and L-SEP in several 
organs, and autoradiography indicated that isotope incorporation ‘nto ethanolamine 
phosphate and SEP was greatest in the kidney and heart. Much less isotope was 
incorporated in SEP isolated from the red and white muscles where the absolute 
amounts of SEP were believed to be greatest. Attempts at the 77 vitro incorporation 
of 32P into t-SEP in a variety of organs were unsuccessful although a small amount 
of isotope was incorporated into 1-SEP in turtle erythrocytes after 12 h incuba- 
tion at 37° (ref. 4). The apparent slow rate of synthesis of L-SEP gave rise to the 
suggestion that the compound was not synthesized from small molecular-weight pre- 
cursors®> 4, 
The interest of the present authors in the work of Roperts and his group arose 
from the structural similarity of SEP and lombricine to which attention had been 
drawn by ENNor AND Morrison?2. Lombricine was discovered by the French group” ° 
in Roche’s laboratory and was isolated in low yield from the earthworm (Lumbricus 
terrestris). On the basis of degradative studies®»® the compound was assigned the follow- 
ing structure: 
References p. 192/193 
