Lysine Metabolism in Neurospora
<p>The lysine requiring mutants of Neurospora crass, when classified by the criteria of symbiotic, specificity of growth requirements, intersterility and genetic recombination, fall into five groups representing at least five loci. Members of two groups are capable of growth on a minimal...
| Summary: | <p>The lysine requiring mutants of Neurospora crass, when
classified by the criteria of symbiotic, specificity
of growth requirements, intersterility and genetic recombination,
fall into five groups representing at least five loci.
Members of two groups are capable of growth on a minimal
medium supplemented with either lysine, ∈-hydroxynorleucine
or α-aminoadipic acid. Members of a third group can utilize
lysine or ∈-hydroxynorleucine, while members of the fourth
and fifth group are unable to grow in the absence of lysine
itself.</p>
<p>The D-isomers of all these amino acids stimulate growth
in the presence of the natural isomers. Nevertheless their
α-keto analogues when added to the medium are without effect.
Since it has been shown that Neurospora has enzymes catalyzing
the interconversions of α-aminoadipic and α-keto-adipic
acids, the nonutilization of the exogenous keto acids
is ascribed to a failure of assimilatory mechanisms.</p>
<p>Investigations of the incorporation of isotopic nitrogen
into the mycelial lysine indicate that both the α and ∈-amino
groups are quite stable. Inasmuch as the nitrogen of
α-aminoadipic acid is labile it is suggested that the degradation
of lysine via that acid is not quantitatively significant.</p>
<p>None of a number of other substances which might be
postulated either as precursors of α-aminoadipic acid or
as intermediates between that acid and lysine has any effect
on growth. Syntheses of several of these compounds are
described.</p>
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