Part I. Synthesis of L-Arnino Acid Oxidase by a Serine- or Glycine-Requiring Strain of Neurospora. Part II. Studies Concerning Multiple Electrophoretic Forms of Tyrosinase in Neurospora
<p>Part I: Synthesis of L-Amino Acid Oxidase by a Serine- or Glycine-Requiring Strain of Neurospora</p> <p>Wild-type cultures of Neurospora crassa growing on minimal medium contain low levels of L-amino acid oxidase, tyrosinase, and nicotinarnide adenine dinucleotide glycohyd...
| Summary: | <p>Part I: Synthesis of L-Amino Acid Oxidase by a Serine- or Glycine-Requiring
Strain of Neurospora</p>
<p>Wild-type cultures of Neurospora crassa growing on minimal
medium contain low levels of L-amino acid oxidase, tyrosinase, and
nicotinarnide adenine dinucleotide glycohydrase (NADase). The enzymes
are derepressed by starvation and by a number of other conditions which
are inhibitory to growth. L-amino acid oxidase is, in addition, induced
by growth on amino acids. A mutant which produces large quantities of
both L-amino acid oxidase and NADase when growing on minimal medium was
investigated. Constitutive synthesis of L-amino acid oxidase was shown
to be inherited as a single gene, called P110, which is separable from
constitutive synthesis of NADase. P110 maps near the centromere on
linkage group IV.</p>
<p>L-amino acid oxidase produced constitutively by P110 was partially
purified and compared to partially purified L-amino acid oxidase
produced by derepressed wild-type cultures. The enzymes are identical
with respect to thermostability and molecular weight as judged by gel
filtration.</p>
<p>The mutant P110 was shown to be an incompletely blocked auxotroph
which requires serine or glycine. None of the enzymes involved
in the synthesis of serine from 3-phosphoglyceric acid or glyceric acid
was found to be deficient in the mutant, however. An investigation of
the free intracellular amino acid pools of P110 indicated that the
mutant is deficient in serine, glycine, and alanine, and accumulates
threonine and homoserine.</p>
<p>The relationship between the amino acid requirement of P110 and
its synthesis of L-amino acid oxidase is discussed.</p>
<p>Part II: Studies Concerning Multiple Electrophoretic Forms of Tyrosinase
in Neurospora</p>
<p>Supernumerary bands shown by some crude tyrosinase preparations
in paper electrophoresis were investigated. Genetic analysis indicated
that the location of the extra bands is determined by the particular T
allele present. The presence of supernumerary bands varies with the
method used to derepress tyrosinase production, and with the duration
of derepression. The extra bands are unstable and may convert to the
major electrophoretic band, suggesting that they result from modification
of a single protein. Attempts to isolate the supernumerary bands
by continuous flow paper electrophoresis or density gradient zonal
electrophoresis were unsuccessful.</p> |
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