Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P01189 (beta-endorphin)
 21,003 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Methyl esterification of pituitary polypeptides by protein methylase II (S-adenosylmethionine:protein-carboxyl O-methyltransferase, EC. 2.1.1.24) has been investigated. Ovine lutropin and adrenocorticotropin (alpha1-39-ACTH) were found to be good methyl acceptor substrates, followed by beta-lipotropin. While the alpha-subunit of lutropin had nearly equal the methyl accepting activity of lutropin, the beta-subunit was devoid of accepting activity. The maximum amount of esterification occurred between 15 and 30 min at 37 degrees C) depending on the methyl acceptor molecule. The rate of the methyl esterification of adrenocorticotropin fragments was also studied. While alpha7-38-ACTH had less than half of alpha1-37-ACTH methyl accepting capacity, alpha1-17-ACTH did not serve as methyl acceptor. However, when a mixture of the two fragments was preincubated, the resulting mixture had full alpha1-39-ACTH activity.
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PMID:Enzymatic methyl esterification of pituitary polypeptides. 21 89

Ovine corticotropin (alpha s-ACTH) was enzymatically methylated with purified calf brain protein methylase II (protein O-methyltransferase; S-adenosyl-L-methionine: protein-carboxyl O-methyltransferase, EC 2.1.1.24) and S-adenosyl-L-[methyl-14C]methionine. After incubation for 60 min at 37 degrees C, 30 mol % of the hormone was methylated on the basis of the [14C]methyl incorporation. In order to assess the location of methylation, the modified peptide was digested with pepsin. Analytical results derived from studies on the peptic digest led to the suggestion that the alpha s-ACTH-(6--28) peptide fragment was esterified. Because there is only one available methylation site at Glu-28, these results indicate that Glu-28 of alpha s-ACTH was specifically methyl esterified to yield [Glu(OMe)28]-alpha s-ACTH.
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PMID:Enzymatic methyl esterification of specific glutamyl residue in corticotropin. 22 92

Deamidation of Asn residues is one of the major chemical pathways of degradation of proteins and peptides. Adrenocorticotropic hormone (ACTH), a 39-amino acid polypeptide with a single Asn residue, was shown in this study to be a useful model polypeptide for the study of the effects of pH and buffer concentration on the rate and pathway of deamidation. The disappearance of ACTH and appearance of deamidated ACTH were monitored by isoelectric focusing (IEF), and ammonia production was monitored spectrophotometrically using a coupled enzymatic assay. Using these analytical methods, the deamidation of ACTH was shown to follow pseudo-first-order kinetics and was dependent on pH and buffer concentrations. The separation of the deamidated ACTHs (Asp-ACTH and isoAsp-ACTH) from ACTH was successful, but attempts to separate Asp-ACTH from isoAsp-ACTH using cation-exchange HPLC and IEF were unsuccessful. Using bovine protein carboxymethyltransferase (PCM), which selectively methylates the carboxyl group of isoAsp residue, the isoAsp-ACTH could be detected at pH 7.0 and 9.6 but not at pH 1.9. These data support the hypothesis that under neutral and alkaline conditions, deamidation of ACTH proceeds through the formation of a cyclic imide intermediate (slow step), followed by its hydrolysis to the Asp-ACTH and isoAsp-ACTH (fast step). Under acidic conditions, the reaction appears to proceed via direct hydrolysis of the Asn residue to form Asp-ACTH without the formation of a cyclic imide intermediate.
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PMID:Chemical pathways of peptide degradation. I. Deamidation of adrenocorticotropic hormone. 216 92