A rapid and efficient method for the purification of tyrosinase from Neurospora

The phenoloxidases of the ascomycete Podospora anserina. XIII. Action and interaction of genes controlling the formation of laccase

1. Eight mutants were isolated following mutagen treatment which are deficient in laccase formation. Seven of these had a pleiotropic effect and exhibited defects in growth rate and in mycelial and sexual morphology. 2. By means of tetrad analysis the mutations were assigned to 6 loci. Three mutations were in the incolora locus, the others were non-allelic. Only two of these loci were closely linked. 3. All genes exhibit numerous interactions. These concern the morphological expression of the laccase genes and also the laccase spectra. 4. The mutants could be separated into four classes on the basis of the amount and type of laccase produced. 5. Five of the loci studied appear to be structural genes because mutations alters the physical properties of the laccase protein. The sixth gene has a regulatory role.

Immunochemical studies on tyrosinase induction in Neurospora

An immunoassay for tyrosinase, using the modified bacteriophage technique, was developed: Tyrosinase of Neurospora was conjugated to bacteriophage T4 using glutaraldehyde as a cross-linking agent. The conjugated phage that survived the coupling process could be inactivated by antiserum raised in rabbits against pure tyrosinase, but not by normal serum. This inactivation was specifically inhibited by pure Neurospora tyrosinase, and the degree of inhibition was proportional to the concentration of tyrosinase within the range of 30-150 ng/ml. Crude mycelial extract possessing tyrosinase activity could similarly inhibit the inactivation of the conjugated phage by the antiserum. To evaluate the tyrosinase content of crude extracts their inhibitory capacity was compared to that of known amounts of pure tyrosinase, and the amounts thus calculated agreed with those predicted from an enzymatic assay. The tyrosinase-bacteriophage immunoassay was used for the quantitation of tyrosinase-antigen in crude extracts of Neurospora cultures that had been induced to form tyrosinase by the addition of ethionine. Enzymatic activity appeared after a lag of several hours, increased for 2-3days and then declined. Immunological assays of these cultures showed: (a) serologically reactive protein started to accumulate upon culture starvation and was evident during the lag period; (b) specific activity (units per mg antigen) was constant throughout induction; (c) at the phase of decrease in mycelial enzyme content, increasing amounts of serologically reactive protein were detected in the medium, indicating that some enzyme was eventually excreted. These results show that the lag is not a qualitatively distinct period, and support the previously forwarded notion that tyrosinase is synthesized de novo upon induction.