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Results for “Protein Methyltransferases”

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At least 19 recordsLinked to original sources
PubMed1975

S-adenosylmethionine:protein methyltransferases in hepatomas.

Protein methylase III (S-adenosylmethionine:proteinlysine methyltransferase; ED 2.1.1.25) and protein methylase I (S-adenosylmethionine:protein-arginine methyltransferase; EC 2.1.1.23) activities were examined in isolated nuclei and cytosol fraction, respectively, from various hepatomas with different growth rates. The enzyme activities of both enzymes paralleled the rates of tumor growth in fast- and moderately growing hepatomas. The parallelism was more evident with protein methylase I than with protein methylase III. While protein methylase III activity was elevated in the fast- to moderately growing hepatomas, the enzyme that is responsible for demethylating proteins, epsilon-alkyllysinase (epsilon-slkyl-L-lysine:oxygen oxidoreductase; EC 1.5.3.4), had an inverse relationship to the rate of tumor growth, thus suggesting a possible physiological antagonism. When isolated rat liver nuclei were methylated in vitro with S-adenosyl-L-[methyl-14 C]methionine as methyl donor, H2SO4-insoluble protein and histones had almost equal amounts of methyl-14 C incorporated. However, amino acid analysis revealed that methylated arginines are the predominant form of radioactivity in the H2SO4-insoluble protein (product of protein methylase I), while methylated lysines are the major methylated amino acids in the histones (product of protein methylase III). Furthermore, the hydrolysate of the H2SO4-insoluble protein showed four unknown radioactivity peaks on the amino acid analyzer in addition to the known methylated arginine and lysine derivatives.

Adenine↗
PubMed1977

Identification of a protein methyltransferase as the cheR gene product in the bacterial sensing system.

Methylation of membrane-bound proteins with apparent molecular weights around 65,000 does not occur in mutants of the generally nonchemotactic cheR class of Salmonella typhimurium. This was shown to be due to the lack of a protein methyltransferase in these mutants by means of an in vitro assay using soluble proteins, membranes, and S-adenosylmethionine as the methyl donor. The methylase from the wild type was purified, characterized, and shown to be of molecular weight 38,000. It is specific for proteins in S. typhimurium and Escherichia coli membranes. The methylase is not required for tumbling but appears to be essential for maintaining the appropriate rate constants and levels of the regulator of the chemotactic response.

Chemotaxis↗
PubMed1977

S-adenosylmethionine: protein-arginine methyltransferase. Purification and mechanism of the enzyme.

Protein methylase I (S-adenosylmethionine: protein-arginine methyltransferase, EC 2.1.1.23) has been purified from calf brain approximately 120-fold with a 14% yield. The final preparation is completely free of any other protein-specific methyltransferases and endogenous substrate protein. The enzyme has an optimum pH of 7.2 and pI value of 5.1. The Km values for S-adenosyl-L-methionine, histone H4, and an ancephalitogenic basic protein are 7.6 X 10(-6), 2.5 X 10(-5), and 7.1 X 10(-5) M, respectively, and the Ki value for S-adenosyl-L-homocysteine is 2.62 X 10(-6) M. The enzyme is highly specific for the arginine residues of protein, and the end products after hydrolysis of the methylated protein are NG,NG-di(asymmetric), NG,N'G-di(symmetric), and NG-monomethylarginine. The ratio of [14C]methyl incorporation into these derivatives by enzyme preparation at varying stages of purification remains unchanged at 40:5:55, strongly indicating that a single enzyme is involved in the synthesis of the three arginine derivatives. The kinetic mechanism of the protein methylase I reaction was studied with the purified enzyme. Initial velocity patterns converging at a point on the extended axis of abscissas were obtained with either histone H4 or S-adenosyl-L-methionine as the varied substrate. Product inhibition by S-adenosyl-L-homocysteine with S-adenosyl-L-methionine as the varied substrate was competitive regardless of whether or not the enzyme was saturated with histone H4. On the other hand, when histone H4 is the variable substrate, noncompetitive inhibition was obtained with S-adenosyl-L-homocysteine under conditions where the enzyme is not saturated with the other substrate, S-adenosyl-L-methionine. These results suggest that the mechanism of the protein methylase I reaction is a Sequential Ordered Bi Bi mechanism with S-adenosyl-L-methionine as the first substrate, histone H4 as the second substrate, methylated histone H4 as the first product, and S-adenosyl-L-homocysteine as the second product released.

Animals↗
PubMed1979

Partial purification and characterization of a protein lysine methyltransferase from plasmodia of Physarum polycephalum.

Plasmodia of Physarum polycephalum have an active protein lysine methyltransferase (S-adenosylmethionine:protein-lysine methyltransferase, EC 2.1.1.43). This enzyme has been purified 40-fold with a 13% yield, and it catalyzes the transfer of methyl groups from S-adenosyl-L-methionine to the epsilon-amino group of lysine residues with formation of N epsilon-mono-, N epsilon-di-, and N epsilon-trimethyllysines in a molar ratio of 4:1:1 based on [14C]methyl incorporation into the methylated lysines. The ratio remains unchanged at all stages of the partial purification, as well as after fractionation by sucrose density gradient centrifugation and gel electrophoresis. The rate of protein methylation is time dependent, enzyme concentration dependent, and requires the presence of a sulfhydryl reducing agent for optimal activity. The enzyme has optimal activity at pH 8 and is inhibited by S-adenosyl-L-homocysteine and EDTA. Lysine-rich and arginine-rich histones serve as the most effective exogenous protein acceptors; P. polycephalum actomyosin is inactive, and chick skeletal myofibrillar proteins are 25% as effective as exogenous mixed histones as substrates. Lysine, polylysine, ribonuclease A, cytochrome c, and bovine serum albumin are not methylated.

Histone-Lysine N-Methyltransferase↗
PubMed2026

Protein arginine methyltransferase (PRMT8) in cancer: Genomic alterations, subcellular dynamics, and clinical implications.

PRMT8 encodes a protein arginine methyltransferase, which is primarily expressed in the brain and nervous system. Several studies have reported its alterations, which have been implicated in various cancers. However, the existing information remains unsystematic and fragmented due to inconsistency in methodology. This review aims to explore PRMT8 gene alterations in humans, their effects on cellular function and physiology, and their clinical implications. We conducted a narrative literature review covering all publications on PRMT8 alterations across different cancer types, their effect on tumour cell characteristics, and their impact on patient prognosis. Reported PRMT8 alterations include mutations, copy number amplifications, and single-nucleotide polymorphisms, which lead to overexpression or downregulation of PRMT8 protein in tumour cells. PRMT8 alterations compromise the efficacy of both chemotherapy and immune checkpoint inhibitor treatment. These alterations enable tumour cells to maintain pluripotency via activation of the PI3K/AKT/SOX2 signalling pathway, thereby promoting cellular proliferation, invasion, and colony formation. Clinically, these PRMT8 alterations drive disease progression and therapy resistance, resulting in poor prognosis and reduced patient survival. These findings underscore the need to incorporate PRMT8 alterations assessment in clinical practice to guide therapeutic decision-making and improve treatment outcomes in affected patient populations.

Humans↗
PubMed1979

Yeast cytochrome c-specific protein-lysine methyltransferase: coordinate regulation with cytochrome c and activities in cyc mutants.

The cytochromes c of fungi and higher plants contain one or two residues of epsilon-N-trimethyllysine, whose biological role is unknown. A cytochrome c-specific S-adenosylmethionine:protein-sysine methyltransferase (methylase) activity was shown to be present in extracts of the bakers' yeast Saccharomyces cerevisiae, and basic kinetic properties of this enzyme are described. The specific activity of the methylase was lower in extracts of cells grown under conditions of catabolite (glucose) repression or anaerobiosis where cytochrome c levels were low, compared with cells grown under derepressed conditions where cytochrome c levels were high. During anaerobic-to-aerobic adaptation, the methylase was induced in parallel with cytochrome c, thus suggesting that the syntheses of cytochrome c and cytochrome c methylase are coordinately regulated. None of the cyc strains surveyed (cyc1, cyc2, cyc3, cyc4, cyc5, and cyc6) had diminished levels of methylase, although some of them were completely or almost completely deficient in cytochrome c.

Cell-Free System↗
PubMed2026

Protein arginine methyltransferases as metabolic regulators: many roles beyond cancer.

Metabolic syndrome (MetS) comprises a cluster of interconnected metabolic abnormalities that collectively elevate the risk of cardiovascular disease and mortality. With its global prevalence escalating, understanding the molecular underpinnings of MetS has become increasingly imperative. Protein arginine methyltransferases (PRMTs), classically studied for their epigenetic functions and oncogenic properties, are now recognized as pivotal regulators of metabolic homeostasis. Emerging research reveals that these enzymes coordinate crucial aspects of cellular metabolism through multiple mechanisms, including methylation of metabolic transcription factors, modulation of nutrient-sensing pathways, and direct regulation of enzymatic activities in glucose and lipid metabolism. This review summarizes current knowledge on the metabolic roles of PRMTs, specifying their roles in the development and function of major metabolic tissues and their associations with various metabolic disorders. We further review how PRMTs influence metabolic processes by modifying key transcriptional networks and signaling cascades through methylation of different substrates. By integrating these insights, we establish PRMTs as central players in metabolic regulation and assess their potential as therapeutic targets for metabolic diseases beyond their established roles in cancer biology, thereby providing a framework for future research and clinical development.

glucose metabolism↗