{"corpus_id":81395640,"paper_sha":"69adbdf91036d6de6e1668e3ca90636a74321f8a","doi":"10.1016/s0021-9258(18)43141-9","arxiv_id":null,"pmid":null,"pmcid":null,"mag_id":38557909,"dblp_id":null,"acl_id":null,"title":"THE ACTIVITY AND CRYSTALLIZATION OF PHOSPHORYLASE b","year":1945,"publication_date":"1945-04-01","venue":"","journal":{"name":"Journal of Biological Chemistry","pages":"341-346","volume":"158"},"journal_issn":null,"journal_title":null,"publication_types":[],"pubmed_pub_types":null,"s2_fields_of_study":["Biology","Chemistry"],"reference_count":1,"citation_count":29,"influential_citation_count":0,"is_open_access":false,"arxiv_categories":null,"arxiv_license":null,"arxiv_journal_ref":null,"mesh_headings":null,"chemicals":null,"comments_corrections":null,"source_flags":1,"s2_open_access_pdf_url":null,"s2_open_access_landing_url":null,"s2_open_access_license":null,"s2_open_access_status":null,"pmc_open_access_pdf_url":null,"pmc_open_access_landing_url":null,"pmc_open_access_license":null,"pmc_open_access_status":null,"unpaywall_open_access_pdf_url":null,"unpaywall_open_access_landing_url":null,"unpaywall_open_access_license":null,"unpaywall_open_access_status":null,"abstract":"It has been found (1) that when phosphorylase a is converted to phosphorylase b by the PR (or prosthetic group-removing) enzyme in a 0.03 M glycerophosphate-cysteine buffer, the phosphorylase activity in the presence of adenylic acid falls only slightly at the time when the activity without adenylic acid approaches zero. This was taken to indicate that phosphorylases a and 6 have the same activity per mg. of protein. Although the experiments have been repeated with the same results, other findings cast doubt on this conclusion. In Fig. 1 is presented a time curve for the action of PR on phosphorylase a and for a control sample of phosphorylase a incubated without PR, both in glycerophosphate-cysteine buffer. The control sample when tested with or without adenylic acid shows a slight rise in activity with time, following which the activity remains constant. This rise has been described previously (2) and is probably due to a time factor in the reduction of the enzyme by cysteine in the presence .of glycerophosphate. The activity in the sample incubated with PR reaches the same height as the control sample when tested with adenylic acid. Thereafter the activity declines at a rate that would make it about 90 per cent of its original value at the time when the activity without adenylic acid approaches zero; that is, when all of the phosphorylase a has been converted to phosphorylase b. Similar results have been obtained with trypsin, when it is acting on phosphorylase a in a glycerophosphate-cysteine buffer of pH 6.2. Glycerophosphate seems to exert a stabilizing influence, because without it there occurs a greater decrease in the phosphorylase activity with adenylic acid than was found in the experiments in Fig. 1. This is shown in Fig. 2, which represents an average curve for several experiments. It may be seen that, when conversion is complete, phosphorylase b has only 77 per cent of the activity of phosphorylase a. Once all the phosphorylase a has been converted to phosphorylase b, no further change in phosphorylase b activity occurs, even when the incubation is continued with very high concentrations of PR, a fact which has been established in several experiments. Similarly, when phos-","claims":[{"public_id":"cl_f3e3f7195d30fd5d50ddd57ac6c872e7","status":"active","text":"Conversion of phosphorylase a to phosphorylase b by the PR enzyme in glycerophosphate-cysteine buffer leaves adenylic-acid-stimulated activity only slightly reduced while activity without adenylic acid falls nearly to zero.","confidence":0.94,"contributors":[{"id":1,"public_id":"12632b8b5f","public_label":"Anonymous (12632b8b5f)","roles":["extraction"],"url":"https://sah.borca.ai/u/12632b8b5f"}],"url":"https://sah.borca.ai/claims/cl_f3e3f7195d30fd5d50ddd57ac6c872e7"},{"public_id":"cl_ea88d133b451746df0b714a7fc0576cb","status":"active","text":"Further incubation with very high concentrations of PR does not cause additional change in phosphorylase b activity once phosphorylase a has been completely converted.","confidence":0.89,"contributors":[{"id":1,"public_id":"12632b8b5f","public_label":"Anonymous 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