chairman's introduction 467 



degree of gelation. If ATP is added following exposure of eggs to higher 

 concentrations of trypsin it may enhance the reversal of the gelation. 



In Ca^~-free solutions of trypsin this latter has a lower gelating effect. 

 Exposure of the eggs to glutathione after pretreatment with trypsin 

 enhances the reversal of gelation. From a number of such experiments it 

 was evident that the gelation is not directly caused by the trypsin treatment 

 but this latter activates an enzyme of the egg cell which has the gelating 

 effect. If the dose (time x concentration) of trypsin is increased other 

 enzymes are activated which cause a reversal of the gelation. Besides the 

 enzymes of cathepsin B type there are at least three other proteolytic 

 enzymes present in the sea urchin egg with their optimum activity around 

 the neutral point, as was demonstrated by my colleague Dr. G. Lundblad 



IxlO 



IxlO' 

 Percent cr/st. trypsin 



2x10 



Fig. I. Simplified curve from Runnstrom [22], showing the effect of pre- 

 treatment of unfertilized eggs with low concentrations of crystalline trypsin. The 

 eggs were fertilized and the number of uncleaved eggs is plotted as a function of 

 the trypsin concentration (duration of pretreatment: 15 min.). The block of 

 cleavage indicates gelation processes in the cytoplasm. If after the trypsin exposure 

 the eggs were transferred to 5 x 10^ M ATP an enhancement or a removal of 

 gelation was observed according to the level of concentration of trypsin. 



[16]. He designates them as Ei, E2 and E3, of which the first and last are 

 SH-enzymes. It is not excluded that the gelating action may be assigned 

 to one of these enzymes and the reversal of gelation to two other enzymes. 

 These results seem to indicate the possibility that changes in consistency 

 of the cytoplasm may be controlled by enzymes of proteolytic character. 



If homogenates of unfertilized eggs were subjected to a treatment with 

 ribonuclease a considerable activation of the proteolytic enzymes occurs. 

 The interpretation was that these enzymes are attached to the ribonucleo- 

 protein granules of the microsome system w^here they probably have been 

 synthesized. 



In conjunction with my colleagues Hagstrom and Low [26] I demon- 

 strated that the same holds true for a factor which gelates the jelly coat 

 surrounding the egg. This coat consists of a complex of polysaccharides 



