Biosynthesis of choline and its incorporation by resting cells of Neurospora crassa.

Attempts have been made to demonstrate the synthesis of choline by respiring
mycelia of N. crassa (wild) from ethanolamine and various methyl precursors
under varied experimental conditions. In no case a net increase in choline content
has been observed. The abUity of the cells to bring about the synthesi.s could be
inferred from the presence of this metabolite in the mycelium harvested from
the chollneless medium. More directly the ability to incorporate C14 from (C14Ha)
methionine or (3-C14) serine has been demonstrated.
Mycelia of both the wild type and the cholineless strai.ns can rapidly incorporate
choline into the cells, the amount incorporated increasing with the concentration
of choline in the suspension medium up to 50 ug./ml. A balance sheet reveals that
during the 4 hr period of incubation much (up to 30 per cent) of the choline was lost
in unaccountable ways. This is not due to oxidation, demethylation, conversion
to trimethylamine or degradations leading to liberation of free ammonia.