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NITROGEN METABOLISM OF YEAST. A CONSIDERATION OF THE MODE OF ASSIMILATION OF AMINO ACIDS
Author(s) -
Thorne R. S. W.
Publication year - 1949
Publication title -
journal of the institute of brewing
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.523
H-Index - 51
eISSN - 2050-0416
pISSN - 0046-9750
DOI - 10.1002/j.2050-0416.1949.tb01492.x
Subject(s) - deamination , amino acid , hydrolysate , yeast , biochemistry , ammonia , chemistry , glutamine , ammonium , casein , salt (chemistry) , transaminase , metabolism , biology , hydrolysis , organic chemistry , enzyme
Yeast growth is much more active on wort than when nitrogen is supplied as an ammonium salt which, in turn, will in general support growth better than do individual amino acids. These facts cannot be explained in terms of the Ehrlich and Stickland mechanisms of deamination, and it is suggested that a third mechanism is involved, namely, that when yeast is supplied with a complex mixture of amino acids it tends to assimilate them intact, with more rapid utilization than if deamination were involved. If a necessary amino acid is lacking, deamination will be required to allow its synthesis from ammonia. The hypothesis is supported by the enhanced values of amino acid mixtures as compared with single amino acids, and by the high rate of growth on casein hydrolysate accompanied by greater availability of sugar for fermentation. Also, the effects of deficiency of pyridoxin (presumed to be involved in deamination) are less marked with the hydrolysate than with single amino acids.