Carboxylmethylation of insulin and glucagon in vitro.
We studied the methyl acceptor capacity of insulin and glucagon in vitro. The levels of carboxylmethylation of pancreatic hormones (dpm x 10(3], 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 corresponding 125I-hormone. Glucagon, but not insulin, seems to be a relatively good substrate for carboxylmethylation.
Mena
P
P
Departamento de Fisiología, Facultad de Medicina, Universidad de Extremadura, Badajoz, Spain.
Barriga
C
C
Timón
J
J
Campillo
J E
JE
D000311:Adrenal Glands / Q000201:enzymology*; D000818:Animals; D002417:Cattle; D005934:Glucagon / Q000378:metabolism*; D007328:Insulin / Q000378:metabolism*; D008745:Methylation; D011496:Protein Methyltransferases / Q000378:metabolism*; D011497:Protein O-Methyltransferase / Q000302:isolation & purification / Q000378:metabolism*; D013379:Substrate Specificity
D007328:Insulin; D005934:Glucagon; D011496:Protein Methyltransferases; D011497:Protein O-Methyltransferase