194
G. L. CANTONI
variety of plants (31), where its formation is greatest during the period
of active vegetative growth. In plants, in aerobic bacteria such as
Fsuedomonas, and in other gram-negative organisms (32, 33) trimethylamine may be derived from choline by an elimination reaction formally
analogous to the formation of dimethyl sulfide from the sulfonium
analog of homobetaine (34) (see Section IV,A,1). In anaerobes on the
other hand (35) Hay ward and Stadtman have observed the reaction
shown in Eq. 8 in which it would appear as if a dismutation of 2 moles
of choline aldehyde is synchronous with cleavage of the onium bond.
H 2 0 + 2 Choline -> 2(CH 3 ) 3 N + CH 3 —CH 2 OH + CH 3 COOH + 2H+
(8)
This reaction may account also for the earlier observations of Dyer and
Wood (36) who found that organic acid was formed in the bacterial
metabolism of choline.
It must of course be quite clear by now that the proposed biogenetic
schemes are rich in speculation and short in evidence. The fundamental
assumption underlying the various hypothetical pathways discussed in
schemes 1, 2, 3, and 4, however, is widely accepted and indeed forms
one of the cornerstones of comparative biochemistry. This assumption
postulates that the living cell utilizes for its biosynthetic purposes only
a relatively small number of reactions, and modifies them according to
its special requirements along a pattern that, in music, is known as
Theme and Variations.
A. BIOCHEMISTRY OF ALIPHATIC QUATERNARY AMMONIUM COMPOUNDS
As pointed out above, knowledge of the biochemistry of aliphatic
quaternary ammonium compounds is sketchy. In some cases, choline, for
instance, an enormous literature has accumulated. In most other cases,
however, little is known beyond the structure of the compound and one
or more sources of origin.
1. Choline
Choline is probably the onium compound with the widest distribution as it is found in almost all living cells, predominantly or perhaps
exclusively in combined form mainly in the phospholipid fraction. The
subject has been recently and repeatedly reviewed (37) and only a few
comments need to be made at this time.
Quantitatively the role of choline as a constituent of the phospholipids of the lecithin and sphingosine type overshadows other possible
functions of choline. Qualitatively, however, choline esters in minute
amounts play a fundamental role in neurophysiology (38, 39). Although
acetylcholine is the best known member of this family it is of interest,
G. L. CANTONI
variety of plants (31), where its formation is greatest during the period
of active vegetative growth. In plants, in aerobic bacteria such as
Fsuedomonas, and in other gram-negative organisms (32, 33) trimethylamine may be derived from choline by an elimination reaction formally
analogous to the formation of dimethyl sulfide from the sulfonium
analog of homobetaine (34) (see Section IV,A,1). In anaerobes on the
other hand (35) Hay ward and Stadtman have observed the reaction
shown in Eq. 8 in which it would appear as if a dismutation of 2 moles
of choline aldehyde is synchronous with cleavage of the onium bond.
H 2 0 + 2 Choline -> 2(CH 3 ) 3 N + CH 3 —CH 2 OH + CH 3 COOH + 2H+
(8)
This reaction may account also for the earlier observations of Dyer and
Wood (36) who found that organic acid was formed in the bacterial
metabolism of choline.
It must of course be quite clear by now that the proposed biogenetic
schemes are rich in speculation and short in evidence. The fundamental
assumption underlying the various hypothetical pathways discussed in
schemes 1, 2, 3, and 4, however, is widely accepted and indeed forms
one of the cornerstones of comparative biochemistry. This assumption
postulates that the living cell utilizes for its biosynthetic purposes only
a relatively small number of reactions, and modifies them according to
its special requirements along a pattern that, in music, is known as
Theme and Variations.
A. BIOCHEMISTRY OF ALIPHATIC QUATERNARY AMMONIUM COMPOUNDS
As pointed out above, knowledge of the biochemistry of aliphatic
quaternary ammonium compounds is sketchy. In some cases, choline, for
instance, an enormous literature has accumulated. In most other cases,
however, little is known beyond the structure of the compound and one
or more sources of origin.
1. Choline
Choline is probably the onium compound with the widest distribution as it is found in almost all living cells, predominantly or perhaps
exclusively in combined form mainly in the phospholipid fraction. The
subject has been recently and repeatedly reviewed (37) and only a few
comments need to be made at this time.
Quantitatively the role of choline as a constituent of the phospholipids of the lecithin and sphingosine type overshadows other possible
functions of choline. Qualitatively, however, choline esters in minute
amounts play a fundamental role in neurophysiology (38, 39). Although
acetylcholine is the best known member of this family it is of interest,