1. The purification of a tyrosinase from cell-free extracts of Xtreptomyces glaucescens is described. The enzyme obtained is homogeneous according to the criteria of ultracentrifuge analysis and polyacrylamide gel electrophoresis.2. An average molecular weight of 29 100 was determined by dodecylsulfate-gel electrophoresis and by sedimentation equilibrium analysis in the ultracentrifuge. The amino acid composition of the pure enzyme is also reported.3. The enzyme contains one atom of copper in the cuprous form per molecule and is strongly inhibited by KCN and 4-nitro-catechol.4. The enzyme shows optimal activity a t pH 6.8; it has an isoelectric point at pH 6.95 and is most stable a t pH 8.0.5 . Variations of K , values between pH 5.0 and 8.9 when L-tyrosine methylester and 3,4-dihydroxy-L-phenylalanine were used as substrate was interpreted by assuming that different ionizable groups are involved in the oxidation of these two substrates. 6. The Michaelis-Menten constants and kcat are strongly dependent on the oxygen concentration for 3,4-dihydroxy-~-phenylalanine and almost independent for L-tyrosine methyl ester. Kinetic parameters obtained for a series of mono-and o-diphenol substrates are also reported. the orthoh-ydroxylation of monophenols to catechols, which is referred to as cresolase activity, and the dehydrogenation of catechols to o-quinones, designated as catecholase activity. Molecular oxygen is the source for the hydroxylation reaction [24] ; for this reason, tyrosinase acting on a monophenol is referred to as a "mixed function oxidase" [25].Since many Streptomyces are able to convert tyrosine to melanin 126-301, and no tyrosinase had been isolated from prokaryotic organisms, the purpose of this work was to purify a tyrosinase from Streptomyces glaucescens and compare its molecular properties with those of tyrosinases from eukaryotic organisms.

No abstract

Z u s ammenf a s s ung.Naturliches (

In der vorlicgenden Arbeit wcrden eine neuartige Gruppe basisch substituicrter Hydrazine sowie verschiedene zur Synthese dicscr Verbindungcn ausgearbcitete Wege beschrieben. Diesc Hydrazin-Derivate zcichnen sich zum Teil durch eigene physiologische Eigenschaften aus, anderseits werden sie fur die Synthesc von phy.;lologisch wirksamen Hetcrocyclen verwendct. Pharmazeutisch-chemisches Laboratorium SANDOZ, Base1 (26. I. 59) 17. Mitteilung I) Aus den Kulturen des Actinomyceten, Stamm ETH. 17474, welcher nach seinen artbestimmenden Merkmalen der Species Streptomyces griseus (KRAINSKI) WAKSJIAN et HEXRICI zugeordnet werden muss2), haben wir ein gelbes, lipophiles, neutrales Antibioticum, das mit keinem in der Literatur beschriebenen Actinomyceten-hletaboliten identisch ist , in kristallisierter Form isolieren konnen. Das Antibioticum liess sich aus den Kulturfiltraten mittels Kthylacetat extrahieren und nach chromatographischer Anreicherung durch Kristallisation und Hochvakuumsublimation in reiner Form gewinncn. Es wurde von uns Holomycilz genannt. 440 400 1:ig. 2. I H.-Absor~lionsspektra ,in K B r (PERKTK-ELMER Zweistrahl-Spektrograph Modell 21)