Summary
We studied the methyl acceptor capacity of insulin and glucagonin vitro. The levels of carboxylmethylation of pancreatic hormones (dpm × 103), when incubated with S-adenosyl-L-(3H-methyl)-methionine as methyl donor and purified protein carboxylmethylase, were: insulin (n=6) 8.1±0.2 and 11.1±1.5 (mean ± SEM) for 0.25 and 1.0 mg/ml, respectively; glucagon (n=6) 17.0±3.2 and 40.2±2.5 (mean ± SEM) for 0.5 and 1.0 mg/ml, respectively. On a molar basis, the methyl acceptor capacity was 1.0 dpm/pmol for insulin and 9.5 dpm/pmol for glucagon. Polyacrylamide gel electrophoresis of carboxylmethylated hormones showed a radioactivity (3H-methyl) peak that co-migrated with the corresponding125I-hormone. Glucagon, but not insulin, seems to be a relatively good substrate for carboxylmethylation.
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Mena, P., Barriga, C., Timón, J. et al. Carboxylmethylation of insulin and glucagonin vitro . Acta diabet. lat 25, 127–131 (1988). https://doi.org/10.1007/BF02581376
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DOI: https://doi.org/10.1007/BF02581376