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Ectoprotein kinase activity of the isolated rat adipocyte. |
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| Authors: | E S Kang R E Gates T M Chiang A H Kang |
| Affiliation: | 1. Department of Pediatrics, University of Tennessee Center for the Health Sciences, Memphis, Tennessee, USA;2. Department of Medicine, University of Tennessee Center for the Health Sciences, Memphis, Tennessee, USA;3. the Collagen Laboratory, Veterans Administration Hospital, Memphis, Tennessee, USA |
| Abstract: | Intact adipocytes exhibit ectoprotein kinase activity as reflected by their ability to catalyze the transfer of the terminal phosphate of (γ-32P) ATP to histone added to a cell suspension. This activity is substrate, time and cell number dependent. Lineweaver-Burk plots gave Km and Vmax values for ATP of 5 × 10?5 M and 7.14 pmoles/min/1.5 × 105 cells. Cyclic AMP but not cyclic GMP in μM concentrations stimulates ectoprotein kinase activity. The controlled tryptic digestion of intact cells results in reduction of ectoprotein kinase activity. This activity is not due to leakage of intracellular protein kinases during the preparative procedure nor to penetration of histone into the cells. Additional phosphoproteins not accessible to endogenous protein kinase activity are also localized on the external surface of the intact fat cell. |
| Keywords: | ATP adenosine 5′-triphosphoric acid cyclic AMP adenosine 3′, 5′ cyclic monophosphoric acid SDS-PAGE sodium dodecyl sulphate-polyacrylamide gel electrophoresis TCA trichloroacetic acid cyclic GMP guanosine 3′, 5′ cyclic monophosphoric acid KRB Krebs Ringer bicarbonate buffer LDH lactate dehydrogenase |
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