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Results for “Protein O-Methyltransferase”

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At least 19 recordsLinked to original sources
PubMed1979

Enzymatic methyl esterification of specific glutamyl residue in corticotropin.

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.

Adrenocorticotropic Hormone↗
PubMed1977

Enzymatic methyl esterification of Escherichia coli ribosomal proteins.

Enzymatic methyl ester formation in Escherichia coli ribosomal proteins was observed. Alkali lability of the methylated proteins and derivatization of the methyl groups as methyl esters of 3,5-dinitrobenzoate indicate the presence of protein methyl esters. The esterification reaction occurs predominantly on the 30S ribosomal subunit, with protein S3 as the major esterified protein. When the purified 30S subunit was used as the methyl acceptor, protein S9 was also found to be esterified. The enzyme responsible for the esterification of free carboxyl groups in proteins, protein methylase II (S-adenosyl-L-methionine:protein carboxyl methyltransferase, EC 2.1.1.24), was identified in E. coli Q13. This enzyme is extremely unstable when compared with that from mammalian origin. By molecular sieve chromatography, E. coli protein methylase II showed multiple peaks, with a major broad peak around 120,000 daltons and several minor peaks in the lower-molecular-weight region. Rechromatography of the major enzyme peak showed activities in several fractions that are much lower in molecular weight. The substrate specificity of the E. coli enzyme is similar to that of the mammalian enzyme. The Km value for S-adenosyl-L-methionine is 1.96 X 10(-6) M, and S-adenosyl-L-homocysteine was found to be a competitive inhibitor, with a Ki value of 1.75 X 10(-6) M.

Chromatography, Gel↗
PubMed1979

Enzymatic methyl esterification of pituitary polypeptides.

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.

Adrenocorticotropic Hormone↗
PubMed1976

Amino acid metabolism.

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Amino Acid Metabolism, Inborn Errors↗
PubMed1978

Enzymatic methylation of carboxyl groups of chromaffin granule membrane proteins.

Carboxyl groups of membrane and soluble proteins from bovine adrenal medulla chromaffin granules were enzymatically methylated. The methylated peptides were resolved using gel electrophoresis under acidic conditions in the presence of N-cetylpyridinium chloride. There was a selective methylation of two groups of membrane peptides which did not correspond to any of the chromaffin granule soluble proteins. Dopamine beta-hydroxylase, an acidic protein accounting for up to 25% of the membrane proteins, was a poor substrate for protein carboxylmethylase. The methyl esters of membrane proteins were more labile than those of the chromaffin granule soluble proteins. At all pH values tested, membrane protein-methyl esters were hydrolyzed three times more rapidly than the soluble protein-methyl esters.

Adrenal Medulla↗
PubMed2026

Proteomic profiling of the aqueous extract from the antennal gland of the Pacific white shrimp, Litopenaeus vannamei.

The antennal gland (AnG) of decapod crustaceans has been proposed as a potential source of bioactive molecules involved in chemical communication; however, its protein composition remains largely unexplored. Here, we present the first reference proteomic map of the aqueous extract from the antennal gland of the Pacific white shrimp Litopenaeus vannamei. Protein extracts from immature and mature females were analyzed using an integrated workflow combining one-dimensional SDS-PAGE, reverse-phase high-performance liquid chromatography (RP-HPLC), and nanoLC-tandem mass spectrometry. Electrophoretic and chromatographic analyses revealed a high degree of qualitative similarity between reproductive stages. SDS-PAGE resolved six major protein bands (∼227, 166, 77, 42, 35, and 17 kDa), most comprising multiple co-migrating proteins as revealed by LC-MS/MS. Hemocyanin was identified as the predominant protein and was detected across several electrophoretic bands. Additional proteins were associated with innate immunity, including β-1,3-glucan-binding protein and coagulable hemolymph protein; reproductive processes, including vitellogenin, spermatogonial stem-cell renewal factor, farnesoic acid O-methyltransferase, estrogen sulfotransferase, and prostaglandin reductase 1; as well as energy metabolism, protein homeostasis, cytoskeletal organization, and intracellular trafficking. Because several identified proteins are widely distributed or known hemolymph components, their detection cannot be assumed to reflect AnG-specific expression or function. Collectively, these findings establish a molecular reference for the L. vannamei AnG and reveal protein components associated with multiple physiological processes. This dataset provides a proteomic framework for future comparative and functional studies aimed at elucidating antennal gland physiology and experimentally evaluating the potential involvement of proteinaceous or peptide-based molecules in chemical communication in decapod crustaceans.

Animals↗
PubMed1977

Organ culture of rat superior cervical ganglia.

The maintenance of adrenergic function has been investigated in organ cultures of adult rat superior cervical ganglia. Tyrosine hydroxylase and monoamine oxidase activities decreased gradually through 72 hours of culture. Dopamine beta-hydroxylase activity gradually increased in the cultured ganglia to 150% of that seen in fresh ganglia after 14 hours in culture. The level of norepinephrine increased in the cultured ganglia to a maximum of 225% of that seen in control ganglia. The increases in both dopamine beta-hydroxylase activity and in norepinephrine levels required protein synthesis but they were not dependent on the presence of nerve growth factor. The accumulation of norepinephrine in the cultured ganglia could not be explained by an increased rate of amine synthesis. Turnover measurements suggest that the accumulation can be explained by a decreased rate of amine metabolism in the cultured ganglia. A comparison of the distribution of amine storage vesicles showed that the number of heavy vesicles was greater in cultured than in fresh ganglia. The results suggest that sympathetic ganglia develop an increased capacity for amine storage in culture and that this leads to an increase in intracellular levels of norepinephrine.

Animals↗
PubMed2026

Enzymatic innovations in Angelica pubescens reveal dual coumarin biosynthetic pathways driving metabolic diversification.

Coumarins are structurally diverse phenylpropanoid derivatives with ecological and pharmacological significance, yet the biosynthetic logic underlying their diversification remains incompletely understood in non-model medicinal plants. Angelica pubescens (Apiaceae), widely used in traditional Chinese medicine, accumulates a rich repertoire of furanocoumarins and dihydrofuranocoumarins, making it an ideal system to investigate this metabolic complexity. Here, we combined chromosome-level genome assembly, transcriptome and metabolite profiling, phylogenetics, and heterologous expression assays to dissect coumarin biosynthesis in A. pubescens. We identified two functionally specialized O-methyltransferases, ApOMT1 and ApOMT2, which catalyze regioselective methylation of xanthotoxol and bergaptol to yield the furanocoumarins xanthotoxin and bergapten. We also characterized ApCYP736A121, a cytochrome P450 enzyme that converts osthenol to the dihydrofuranocoumarin columbianetin via a previously unknown mechanism. Gene expression and metabolite accumulation patterns across tissues and developmental stages revealed functional partitioning among pathway branches. Phylogenetic and syntenic analyses indicated that ApOMT1 and ApOMT2 arose through subfunctionalization following gene duplication, whereas ApCYP736A121 evolved via neofunctionalization from a distantly related CYP736 ancestor. Together, our findings uncover dual biosynthetic routes to structurally distinct coumarins in A. pubescens and provide insights into the evolutionary mechanisms contributing to metabolic innovation in Apiaceae. This work lays a foundation for future efforts to engineer coumarin pathways and understand their ecological functions in medicinal plants.

Coumarins↗
PubMed1976

Biochemical differentiation of mechanically dissociated mammalian brain in aggregating cell culture.

Mouse and rat brain cells were dissociated by a simple mechanical sieving technique and studied in culture for the formation of aggregates and the activities of choline acetyltransferase, acetylcholinesterase, glutamic acid decarboxylase, tyrosine 3-monooxygenase, aromatic L-amino acid decarboxylase, catechol methyltransferase, and monoamine oxidase. Cells from fetal and neonatal tissue formed aggregates but not cells from tissue older than two days after birth. The pattern of development of enzyme activities in these aggregates varied with the age of starting tissue. The highest levels of specific activity for the neuron-specific enzymes were found after 3-4 weeks in culture for aggregates of cells derived from relatively undeveloped brains.

Acetylcholinesterase↗