. Biological structure and function; proceedings. Biochemistry; Cytology. 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
. Biological structure and function; proceedings. Biochemistry; Cytology. 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 w
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