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1. A chymotrypsin-like proteolytic activity was found both in unfertilized eggs and in embryos of Bufo bufo. 2. A dramatical change of activity can be observed in the course of embryonic development. The activity rapidly increases after fertilization up to the stage 9 followed by a fall to a level close to unfertilized eggs. 3. Gel chromatography analysis reveals, in all stages of development, the presence of a single peak of proteinase activity characterized by a very high molecular mass. 4. Proteinase activity, found change during the development of Bufo bufo, was characterized by substrate specificity, protease inhibitor and pH effect. All results obtained suggest that the chymotrypsin-like activity can be assigned to the multicatalytic proteinase.

Tyrosine aminotransferase multiple forms occurring in rat liver are not present in all mammalian species. Among animals examined only rat and mouse liver possesses multiple forms of tyrosine aminotransferase; in guinea-pig, rabbit, bovine and sheep liver the enzyme occurs in a single form. The presence of lysosomal converting factor (cathepsin T), responsible for arising of multiple forms of tyrosine aminotransferase in rat liver, has been checked in another species lacking enzyme subforms. Lysosomal extracts of guinea-pig liver interconverts tyrosine aminotransferase from rat liver; lysosomal extracts of rat liver does not generate multiple forms of the enzyme from guinea-pig liver. It has been concluded that in some animals hepatic tyrosine aminotransferase is resistant to the proteolytic cleavage by lysosomal cathepsin T.