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Protein phosphorylation is one of the most ubiquitous and important types of post-translational modification for the regulation of cell function. The importance of two-component histidine kinases in bacteria, fungi and plants has long been recognised. In mammals, the regulatory roles of serine/threonine and tyrosine kinases have attracted most attention. However, the existence of histidine kinases in mammalian cells has been known for many years, although little is still understood about their biological roles by comparison with the hydroxyamino acid kinases. In addition, with the exception of NDP kinase, other mammalian histidine kinases remain to be identified and characterised. NDP kinase is a multifunctional enzyme that appears to act as a protein histidine kinase and as such, to regulate the activation of some G-proteins. Histone H4 histidine kinase activity has been shown to correlate with cellular proliferation and there is evidence that it is an oncodevelopmental marker in liver. This review mainly concentrates on describing recent research on these two types of histidine kinase. Developments in methods for the detection and assay of histidine kinases, including mass spectrometric methods for the detection of phosphohistidines in proteins and in-gel kinase assays for histone H4 histidine kinases, are described. Little is known about inhibitors of mammalian histidine kinases, although there is much interest in two-component histidine kinase inhibitors as potential antibiotics. The inhibition of a histone H4 histidine kinase by genistein is described and that of two-component histidine kinase inhibitors of structurally-related mammalian protein kinases. In addition, recent findings concerning mammalian protein histidine phosphatases are briefly described.  相似文献   

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o-Phthalaldehyde (OPT) reacts with many biogenic compounds such as spermidine, histamine, histidine and peptides with NH2-terminal histidine, yielding intensely fluorescent condensation products. This communication examines the reaction conditions for the OPT-induced fluorescence of histidine and peptides with NH2-terminal histidine for the purpose of improving the sensitivity as well as the specificity of the assay of these compounds. Reaction with OPT at pH 11.2–11.5 and at 40°C for 10 min was found to be optimal for histidine. After cooling, the fluorescence was read at 360440nm (uncorrected instrument values). The method measures as little as 4–5 ng/ml. Peptides with NH2-terminal histidine were found to interfere with the assay whereas histamine, histidinol and spermidine did not. The optimum reaction and assay conditions for the OPT-induced fluorescence of the histidyl-dipeptides varied markedly from one peptide to another. As a group peptides with NH2-terminal histidine are best assayed by condensation with OPT at pH 11.8 at room temperature and with a reaction time of 30 min. Fluorescence should be read before as well as after acidification to pH 2.5. Details are given for the assay of individual histidyl-dipeptides.  相似文献   

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Immuno-cross-reactivity between histidine decarboxylase (HDC) and dopa decarboxylase (DDC) was investigated. By comparing the cDNA sequences of rat HDC with rat and guinea-pig DDCs, we found a region that may possibly be related to the cross-reactivity of anti-rat HDC antibody with guinea-pig DDC. The peptide encoded by this region was synthesized and anti-peptide antibody was prepared. We also purified HDC and DDC homogeniously from fetal rat liver and guinea-pig liver, respectively. On immunoblotting, anti-peptide antibody recognized both rat HDC and guinea-pig DDC. Anti-HDC polyclonal antibody which also recognizes both enzymes detected only rat HDC when it was absorbed by the peptide. This result indicates that this region is responsible for the immuno-cross-reactivity of anti-rat HDC antibody with guinea-pig DDC.  相似文献   

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Abstract— Microassays are described for histamine, histidine, and the activities of the enzymes histidine decarboxylase (EC 4.1.1.22) and histamine niethyltransferase (EC 2.1.1.8) in brain tissue. The enzymic-isotopic microassay for histamine is based on the methylation of tissue histamine by added histamine methyl-transferase and [14C]- or [3H]-labelled S-adenosyl-l -methionine. In a double-isotopic form of the assay, a tracer of [3H]histamine is employed along with [14C]S-adenosyl-l -methionine, and the ratio [14C]:[3H] reflects the amount of histamine in the sample. Because the methylation of histamine is uniform in brain samples studied, a single isotopic assay with [3H]S-adenosyl-l -methionine as the methyl donor is possible and increases sensitivity, so that 10 pg of tissue histamine can be estimated reliably. The assay for histidine involves decarboxylation of histidine by a bacterial histidine decarboxylase and measurement of the histamine formed by the enzymicisotopic procedure. In the histidine decarboxylase assay, histamine synthesized from added histidine is measured. The assay for histamine methyltransferase involves measuring the formation of [14C]methylhistamine with [14C]S-adenosyl-l -methionine serving as the methyl donor.  相似文献   

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Compartmentation in histidine biosynthesis   总被引:2,自引:0,他引:2  
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The existence of protein kinases, known as histidine kinases, which phosphorylate their substrates on histidine residues has been well documented in bacteria and also in lower eukaryotes such as yeast and plants. Their biological roles in cellular signalling pathways within these organisms have also been well characterised. The evidence for the existence of such enzymes in mammalian cells is much less well established and little has been determined about their cellular functions. The aim of the current review is to present a summary of what is known about mammalian histidine kinases. In addition, by consideration of the chemistry of phosphohistidine, what is currently known of some mammalian histidine kinases and the way in which they act in bacteria and other eukaryotes, a general role for mammalian histidine kinases is proposed. A histidine kinase phosphorylates a substrate protein, by virtue of the relatively high free energy of hydrolysis of phosphohistidine the phosphate group is easily transferred to either a small molecule or another protein with which the phosphorylated substrate protein specifically interacts. This allows a signalling process to occur, which may be downregulated by the action of phosphatases. Given the known importance of protein phosphorylation to the regulation of almost all aspects of cellular function, the investigation of the largely unexplored area of histidine phosphorylation in mammalian cells is likely to provide a greater understanding of cellular action and possibly provide a new set of therapeutic drug targets.  相似文献   

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Summary The prebiotic formation of histidine (His) has been accomplished experimentally by the reacton of erythrose with formamidine followed by a Strecker synthesis. In the first step of this reaction sequence, the formation of imidazole-4-acetaldehyde took place by the condensation of erythrose and formamidine, two compounds that are known to be formed under prebiotic conditions. In a second step, the imidazole-4-acetaldehyde was converted to His, without isolation of the reaction products by adding HCN and ammonia to the reaction mixture. LC, HPLC, thermospray liquid chromatography-mass spectrometry, and tandem mass spectrometry were used to identify the product, which was obtained in a yield of 3.5% based on the ratio of His/erythrose. This is a new chemical synthesis of one of the basic amino acids which has not been synthesized prebiotically until now.  相似文献   

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Cells synthesize proteins using 20 standard amino acids and expand their biochemical repertoire through intricate enzyme-mediated post-translational modifications (PTMs). PTMs can either be static and represent protein editing events or be dynamically regulated as a part of a cellular response to specific stimuli. Protein histidine methylation (Hme) was an elusive PTM for over 5 decades and has only recently attracted considerable attention through discoveries concerning its enzymology, extent, and function. Here, we review the status of the Hme field and discuss the implications of Hme in physiological and cellular processes. We also review the experimental toolbox for analysis of Hme and discuss the strengths and weaknesses of different experimental approaches. The findings discussed in this review demonstrate that Hme is widespread across cells and tissues and functionally regulates key cellular processes such as cytoskeletal dynamics and protein translation. Collectively, the findings discussed here showcase Hme as a regulator of key cellular functions and highlight the regulation of this modification as an emerging field of biological research.  相似文献   

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