Genetic and Biochemical Studies of Tyrosinase in Neurospora and Laccase in Neurospora

Citation

Sueoka, Noburu (1959) Genetic and Biochemical Studies of Tyrosinase in Neurospora and Laccase in Neurospora. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/1G65-FS46. https://resolver.caltech.edu/CaltechETD:etd-02172006-105349

Abstract

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Part I: Genetic and Biochemical Studies of Tyrosinase in Neurospora

1) A new form of tyrosinase of Neurospora crassa (Sing-2) was found, which has different electrophoretic behavior and thermostability from the three previously known forms ([...], [...] and [...]).

2) The characteristics of the new form are determined by the single locus, T, which also controls the characteristics of the other forms.

3) The kinetics of thermal inactivation of the different tyrosinases were studied in detail at different temperatures.

4) Two tyrosinaseless genes (ty-l and ty-2) are independent from each other and from the T-locus, and both of them are epistatic to the T-locus.

5) Heterocaryons of the following genotypes were produced. [...]. It was found that a) the ty-1 allele is recessive to its normal form, [...], b) Het.B and Het.D produce a mixture of both forms of tyrosinase determined by their genotypes, and c) the ratio of the two enzyme forms produced corresponds to the ratio of the two component nuclei in the heterocaryons.

6) The significance of the present findings for the gene-enzyme relationship is discussed.

Part II: Laccase in Neurospora

The "second phenol oxidase" in Neurospora reported by Horowitz and Fling (1953) was further studied.

1) The enzyme was purified, characterized as to substrate specificity, inhibitor spectrum, and pH optimum, and identified as a laccase.

2) Production of laccase shows wide variability among different strains of Neurospora and is influenced greatly by external factors, such as temperature, concentrations of sulfur and copper of the medium.

3) Immunological studies show that there is no serological similarity between laccase and tyrosinase of Neurospora.

4) Inducibility of laccase in Neurospora is a variable character, but seems to be strain specific.

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