These experiments indicate that cellular aggregation of the dissociated, glutaraldehyde-fixed, sponge cells depends primarily on the presence of intact disulfide groups and on protein integrity. The importance of the dithiol groups in the process suggests the need for an investigation of cysteine and disulfide linkages in the cell-binding protein. It is suggestive that our aminoacid analysis of acid hydrolyzates of six sponge extracts revealed the presence of cysteic acid and cysteine (18).

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... oliash et al. (9) found that each molecule of glycoprotein in their purified aggregating principle contained 3 moles of sulfate. However, presence of cysteine was not determined. Although none of the glycosidases destroyed the activity of the crude extract, the participation of sugars in the mechanism of the cell aggregation cannot be ruled out definitively because release of sugars has not been shown to occur without impairing the aggregating activity of the extract. However, because one of the enzyme mixtures (clostridial glycosidases) used is very active in removing sugars in other related cell-surface systems (14, 19), one could assume that such a removal, complete or incomplete, took place in our material. . 13. The ribonuclease B, deoxyribonuclease I, leucine aminopeptidase, carboxypeptidase A, Clostridium histolyticum collagenase, papain, and elastase were obtained from the Worth-These experiments indicate that cellular aggregation of the dissociated, glutaraldehyde-fixed, sponge cells depends primarily on the presence of intact disulfide groups and on protein integrity. The importance of the dithiol groups in the process suggests the need for an investigation of cysteine and disulfide linkages in the cell-binding protein. It is suggestive that our aminoacid analysis of acid hydrolyzates of six sponge extracts revealed the presence of cysteic acid and cysteine (18). Margoliash et al. (9) found that each molecule of glycoprotein in their purified aggregating principle contained 3 moles of sulfate. However, presence of cysteine was not determined. Although none of the glycosidases destroyed the activity of the crude extract, the participation of sugars in the mechanism of the cell aggregation cannot be ruled out definitively because release of sugars has not been shown to occur without impairing the aggregating activity of the extract. However, because one of the enzyme mixtures (clostridial glycosidases) used is very active in removing sugars in other related cell-surface systems (14, 19), one could assume that such a removal, complete or incomplete, took place in our material. . 13. The ribonuclease B, deoxyribonuclease I, leucine aminopeptidase, carboxypeptidase A, Clostridium histolyticum collagenase, papain, and elastase were obtained from the Worthington Biochemical Corp., Freehold, N.J.; the wheat germ lipase, egg white muramidase, rennin, thrombin, trypsin, and fibrinolysin from Mann Research Laboratories, New York, N.Y.; the wheat germ acid phosphatase and type 1 calf intestinal mucosa 14 JANUARY 1966 ington Biochemical Corp., Freehold, N.J.; the wheat germ lipase, egg white muramidase, rennin, thrombin, trypsin, and fibrinolysin from Mann Research Laboratories, New York, N.Y.; the wheat germ acid phosphatase and type 1 calf intestinal mucosa 14 JANUARY 1966 alkaline phosphatase from Sigma Chemical Co., St. Louis, Mo.; the alpha amylase and beta glucuronidase from Nutritional Biochemicals Corp., Cleveland, Ohio; the alpha chymotrypsin from General Biochemicals,