202
G. L. CANTONI
DPNase is found primarily in the conidia (92), which, as noted above
for C. purpurea, are also rich in the ergothioneine-forming system.
III. Heterocyclic Onium Compounds
A. SATURATED HETEROCYCLIC COMPOUNDS
1. Pyrrole Derivatives
Stachydrine is found in a variety of plant materials, sometimes in
high concentration as in orange leaves (13 /xmoles per gram dry weight)
(93) and generally accompanied by its higher homolog homostachydrine, the N-dimethylbetaine of pipecolic acid. The biogenesis of
stachydrine has been investigated in alfalfa seedings (94) and a number of interesting features have emerged. It might be expected that
proline would be the precursor of the pyrrole ring of stachydrine and
some support for this hypothesis has been obtained. It has been found
that administration of ornithine-C
14 and pyridoxal resulted in labeling
of both proline and stachydrine. However, the degree of C
14 incorporation was small and clearly such results are indirect and far from compelling. More information is available as to the origin of the methyl
groups. This was studied by measuring the incorporation of the methyl
group of methionine into stachydrine. In young seedlings (15 days old)
no incorporation of the methyl group of methionine was observed unless the nutrient medium was supplemented with folic acid (in addition
to methyl-labeled methionine). Interpretation of these findings is difficult since no comparable data are available as to the rate and extent
of incorporation of formate or other compounds which can serve as
precursors of "one-carbon fragments." It is generally thought that folic
acid coenzymes are not involved in transmethylation reaction, whereas
it is well established that the de novo synthesis of a methyl group from
one-carbon precursors requires the participation of tetrahydrofolic acid
or of a compound derived from it (95). Therefore at the present time
the best conclusion that may be drawn from the results of Wiehler and
Marion (94) suggests that the biosynthesis of stachydrine, like the
synthesis of choline, involves both de novo synthesis of a methyl group
and transfer of the preformed methyl group of methionine. Although
nothing is known about the biogenesis of betonicine, turicine, and
homostachydrine, it may be presumed that it will follow the same
pattern.
Upon heating, stachydrine undergoes a "Willstatter rearrangement"
to the isomeric methylester of hygric acid. Hygric acid itself is found
as a constituent in the nucleus of a great many alkaloids.
G. L. CANTONI
DPNase is found primarily in the conidia (92), which, as noted above
for C. purpurea, are also rich in the ergothioneine-forming system.
III. Heterocyclic Onium Compounds
A. SATURATED HETEROCYCLIC COMPOUNDS
1. Pyrrole Derivatives
Stachydrine is found in a variety of plant materials, sometimes in
high concentration as in orange leaves (13 /xmoles per gram dry weight)
(93) and generally accompanied by its higher homolog homostachydrine, the N-dimethylbetaine of pipecolic acid. The biogenesis of
stachydrine has been investigated in alfalfa seedings (94) and a number of interesting features have emerged. It might be expected that
proline would be the precursor of the pyrrole ring of stachydrine and
some support for this hypothesis has been obtained. It has been found
that administration of ornithine-C
14 and pyridoxal resulted in labeling
of both proline and stachydrine. However, the degree of C
14 incorporation was small and clearly such results are indirect and far from compelling. More information is available as to the origin of the methyl
groups. This was studied by measuring the incorporation of the methyl
group of methionine into stachydrine. In young seedlings (15 days old)
no incorporation of the methyl group of methionine was observed unless the nutrient medium was supplemented with folic acid (in addition
to methyl-labeled methionine). Interpretation of these findings is difficult since no comparable data are available as to the rate and extent
of incorporation of formate or other compounds which can serve as
precursors of "one-carbon fragments." It is generally thought that folic
acid coenzymes are not involved in transmethylation reaction, whereas
it is well established that the de novo synthesis of a methyl group from
one-carbon precursors requires the participation of tetrahydrofolic acid
or of a compound derived from it (95). Therefore at the present time
the best conclusion that may be drawn from the results of Wiehler and
Marion (94) suggests that the biosynthesis of stachydrine, like the
synthesis of choline, involves both de novo synthesis of a methyl group
and transfer of the preformed methyl group of methionine. Although
nothing is known about the biogenesis of betonicine, turicine, and
homostachydrine, it may be presumed that it will follow the same
pattern.
Upon heating, stachydrine undergoes a "Willstatter rearrangement"
to the isomeric methylester of hygric acid. Hygric acid itself is found
as a constituent in the nucleus of a great many alkaloids.