Hemocyanins in spiders, X. Limited proteolysis of chain e of Eurypelma hemocyanin and partial sequence of two large fragments

The polypeptide chain e of the homocyanin from the spider Eurypelma californicum was isolated by ion exchange chromatography. Incubation of the undenatured protein with chymotrypsin, subtilisin, or trypsin resulted in a small number of large fragments which were easily isolated after denaturation. Of the chymotryptic peptides e-Chn-29 was found to be N-terminal, and e-Chn-42 C-terminal. These peptides were characterized by their N-terminal amino acid sequences. The N-terminal sequence of subunit e shows homologies with other arthropod hemocyanins.

Novel opioid peptides derived from casein (beta-casomorphins). I. Isolation from bovine casein peptone

A material which displayed opioid activity in the guinea pig ileum longitudinal muscle-myenteric plexus preparation was extracted from an enzymatic casein digest into chloroform/methanol. The extract was roughly purified by adsorption/desorption procedures using charcoal and Amberlite XAD-2 resin as adsorbents. A high degree of purity was achieved by high-pressure liquid chromatography of the material on muBondapak C18 and mu-Porasil columns and finally by gel filtration chromatography on a Bio-Gel P-2 column. Several pronase-resistant compounds with opioid activity were obtained.

Novel opioid peptides derived from casein (beta-casomorphins). II. Structure of active components from bovine casein peptone

Material with opioid activity had been isolated from an enzymatic casein digest. It was shown to contain a pure heptapeptide with the sequence Tyr-Pro-Phe-Pro-Gly-Pro-Ile. The identity between the opioid principle and the peptide was proven by the fact that chemical reagents or enzymes effecting one would effect the other. After carboxypeptidase Y digestion a pentapeptide, Tyr-Pro-Phe-Pro-Gly, could be isolated; this peptide showed a higher opioid activity than the heptapeptide. The opioid peptides were highly resistant towards proteolysis, even by pronase. The sequence of the hepatapeptide identified it as a fragment of bovine beta-casein. Therefore it was named beta-casomorphin.

Carbohydrate linkage site in the beta-chain of human fibrin

The beta-chain of fibrin was cleaved with trypsin or cyanogen bromide. Carbohydrate containing fragments were isolated by affinity chromatography on concanavalin A-agarose. The fragments were analysed for amino acid sequence and for amino and carbohydrate composition. The sequence of 21 amino acid residues around the carbohydrate attachment point was determined. The carbohydrate carrying amino acid was identified as aspartic acid/asparagine.