{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,13]],"date-time":"2026-02-13T16:01:15Z","timestamp":1770998475770,"version":"3.50.1"},"reference-count":0,"publisher":"Portland Press Ltd.","issue":"3","content-domain":{"domain":["portlandpress.com"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[1988,12,15]]},"abstract":"<jats:p>Calmodulin-dependent protein phosphatase has been proposed to be an important phosphotyrosyl-protein phosphatase. The ability of the enzyme to attack autophosphorylated insulin receptor was examined and compared with the known ability of the enzyme to act on autophosphorylated epidermal-growth-factor (EGF) receptor. Purified calmodulin-dependent protein phosphatase was shown to catalyse the complete dephosphorylation of phosphotyrosyl-(insulin receptor). When compared at similar concentrations, 32P-labelled EGF receptor was dephosphorylated at greater than 3 times the rate of 32P-labelled insulin receptor; both dephosphorylations exhibited similar dependence on metal ions and calmodulin. Native phosphotyrosyl-protein phosphatases in cell extracts were also characterized. With rat liver, heart or brain, most (75%) of the native phosphatase activity against both 32P-labelled insulin and EGF receptors was recovered in the particulate fraction of the cell, with only 25% in the soluble fraction. This subcellular distribution contrasts with results of previous studies using artificial substrates, which found most of the phosphotyrosyl-protein phosphatase activity in the soluble fraction of the cell. Properties of particulate and soluble phosphatase activity against 32P-labelled insulin and EGF receptors are reported. The contribution of calmodulin-dependent protein phosphatase activity to phosphotyrosyl-protein phosphatase activity in cell fractions was determined by utilizing the unique metal-ion dependence of calmodulin-dependent protein phosphatase. Whereas Ni2+ (1 mM) markedly activated the calmodulin-dependent protein phosphatase, it was found to inhibit potently both particulate and soluble phosphotyrosyl-protein phosphatase activity. In fractions from rat liver, brain and heart, total phosphotyrosyl-protein phosphatase activity against both 32P-labelled receptors was inhibited by 99.5 +\/- 6% (mean +\/- S.E.M., 30 observations) by Ni2+. Results of Ni2+ inhibition studies were confirmed by other methods. It is concluded that in cell extracts phosphotyrosyl-protein phosphatases other than calmodulin-dependent protein phosphatase are the major phosphotyrosyl-(insulin receptor) and -(EGF receptor) phosphatases.<\/jats:p>","DOI":"10.1042\/bj2560893","type":"journal-article","created":{"date-parts":[[2015,8,10]],"date-time":"2015-08-10T21:12:39Z","timestamp":1439241159000},"page":"893-902","update-policy":"https:\/\/doi.org\/10.1042\/crossmark_policy","source":"Crossref","is-referenced-by-count":29,"title":["Insulin-receptor phosphotyrosyl-protein phosphatases"],"prefix":"10.1042","volume":"256","author":[{"given":"M J","family":"King","sequence":"first","affiliation":[{"name":"Department of Biochemistry, School of Biochemical and Physiological Sciences, University of Southampton, Bassett Crescent East, Southampton S09 3TU, U.K."}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"G J","family":"Sale","sequence":"additional","affiliation":[{"name":"Department of Biochemistry, School of Biochemical and Physiological Sciences, University of Southampton, Bassett Crescent East, Southampton S09 3TU, U.K."}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"288","container-title":["Biochemical Journal"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/portlandpress.com\/biochemj\/article-pdf\/256\/3\/893\/596494\/bj2560893.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/portlandpress.com\/biochemj\/article-pdf\/256\/3\/893\/596494\/bj2560893.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2021,11,25]],"date-time":"2021-11-25T18:19:32Z","timestamp":1637864372000},"score":1,"resource":{"primary":{"URL":"https:\/\/portlandpress.com\/biochemj\/article\/256\/3\/893\/25378\/Insulin-receptor-phosphotyrosyl-protein"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[1988,12,15]]},"references-count":0,"journal-issue":{"issue":"3","published-print":{"date-parts":[[1988,12,15]]}},"URL":"https:\/\/doi.org\/10.1042\/bj2560893","relation":{},"ISSN":["0264-6021","1470-8728"],"issn-type":[{"value":"0264-6021","type":"print"},{"value":"1470-8728","type":"electronic"}],"subject":[],"published":{"date-parts":[[1988,12,15]]}}}