CHEMICAL ANALYSIS OF TOAD EGG-JELLY IN RELATION TO ITS 'SPERM-CAPACITATING' ACTIVITY

In an attempt to characterize a factor in anuran egg-jelly that is essential for fertilization, dejellied, non-fertilizable eggs of the toad, Bufo bufo, were inseminated in the following jelly preparations: jelly solubilized by KCN followed by dialysis (Dialyzed jelly: DJ), jelly solubilized by ultraviolet irradiation (UVJ), a diffusible factor released from jelly coat into deionized water (DF), the dialyzable fraction of DF (DFD), and the non-dialyzable fraction of DF (DFR). It was found that all the preparations except DFR are active in supporting the fertilization of dejellied eggs. DFD is thermo-stable, and characterized by a rise in pH accompanying increase in concentration. DF obtained from Rana japonica also capacitated the fertilization of dejellied Bufo eggs. Chemical analyses indicated that DJ, UVJ, DF and DFR contain various amounts of fucose, hexoses, hexosamines, and proteins. Sialic acid was present in DJ and UVJ, but not in DF. In DFD, only hexoses and proteins were detectable to a measurable degree. A salient feature of the paper chromatographic analyses was the predominance in DFD of an unspecified reducing sugar which was found in common in all the preparations with fertilization-supporting activity. Gel-filtration in combination with bioassay for fertilization led to the isolation of the active substance, which had a molecular weight of less than 500, and was characterized by a basic nature and the presence of a reducing sugar. The possible importance in fertilization of this small molecular weight jelly component is stressed, together with the suggestion that the component represents some terminal group of the jelly macromolecule in either diffusible or non-diffusible form.