Effect of ascorbate and copper on rate serum albumin
1992
Casella, M.L.A. | Clifford, A. | Whitaker, J.R.
It was recently reported by us that the histidine content of pure bovine serum albumin decreased from 15.6 to 2.2 residues per mol when incubated aerobically with 5 mM ascorbate and 0.8 mM copper sulfate at pH 6.5, 25 degrees C and 22 h in a model experiment. The purpose of the present research was to determine if ascorbate and copper ions decrease the histidine content of rat serum albumin under in vitro and in vivo conditions. The present research showed that histidine residues of rat plasma albumin were less susceptible to destruction than those of bovine serum albumin. Previously isolated rat serum albumin lost 12.2 of 16.6 histidine residues per mol after 24 h incubation with 50 mM ascorbate-8 mM copper sulfate at pH 7.0 and 37 degrees C. When fresh rat plasma was incubated under identical conditions with 50 mM ascorbate-8 mM copper sulfate and the albumin subsequently isolated the histidine lost was 6.4 of the 16.6 residues. No loss of histidine occurred in either experiment under anaerobic conditions (N2). When incubated for 5 h at 37 degrees C and pH 7 with 0.5, 1.0 and 3.0 mM ascorbate-8 mM copper sulfate, fresh rat plasma albumin lost 2.6, 2.9 and 2.8 histidine residues, respectively. When rats were incubated with ascorbate-copper sulfate (50 and 8 mM final concentrations, respectively), 1.2 histidine residues were lost after 2 h.
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