Characterization of the histidine decarboxylase gene of Staphylococcus epidermidis TYH1 coded on the staphylococcal cassette chromosome

Histamine production from histidine in fermented food results in food spoilage, and is harmful to consumers. From fish-miso, we have isolated a new bacterial strain Staphylococcus epidermidis TYH1, which produced histamine under acidic condition in the medium supplemented with glucose. Using oligonucleotides deduced from the histidine decarboxylase gene (hdcA) of Lactobacillus hilgardii, about 14-kbp DNA region of the TYH1 genome was cloned and sequenced. This region contained two putative genes hdcA(TYH1) and hdcP(TYH1) encoding proteins HdcA(TYH1) (310 amino acid residues) and HdcP(TYH1) (495 residues), respectively. Nucleotide sequence around this hdc cluster showed similarity to SCCpbp4 region of S. epidermidis ATCC 12228. Downstream of the cluster, ccrA, ccrB (Type II, respectively) and pbp4 were located. The CcrA and CcrB proteins catalyzed excision of the hdc cluster from the TYH1 chromosome, upon introduction into the TYH1 strain via multicopy plasmid. When hdcA(TYH1) was expressed in Staphylococcus warneri M, histamine was extracellularly accumulated in dependence on exogenous histidine. These results indicate that the gene encoding a histidine decarboxylase resides in a movable genetic element, SCC. This new element is designated as SCChdc.     

Histamine-producing pathway encoded on an unstable plasmid in Lactobacillus hilgardii 0006

Histamine production from histidine in fermented food products by lactic acid bacteria results in food spoilage and is harmful to consumers. We have isolated a histamine-producing lactic acid bacterium, Lactobacillus hilgardii strain IOEB 0006, which could retain or lose the ability to produce histamine depending on culture conditions. The hdcA gene, coding for the histidine decarboxylase of L. hilgardii IOEB 0006, was located on an 80-kb plasmid that proved to be unstable. Sequencing of the hdcA locus disclosed a four-gene cluster encoding the histidine decarboxylase, a protein of unknown function, a histidyl-tRNA synthetase, and a protein, which we named HdcP, showing similarities to integral membrane transporters driving substrate/product exchange. The gene coding for HdcP was cloned downstream of a sequence specifying a histidine tag and expressed in Lactococcus lactis. The recombinant HdcP could drive the uptake of histidine into the cell and the exchange of histidine and histamine. The combination of HdcP and the histidine decarboxylase forms a typical bacterial decarboxylation pathway that may generate metabolic energy or be involved in the acid stress response. Analyses of sequences present in databases suggest that the other two proteins have dispensable functions. These results describe for the first time the genes encoding a histamine-producing pathway and provide clues to the parsimonious distribution and the instability of histamine-producing lactic acid bacteria.     

Molecular cloning and functional characterization of a sucrose isomerase (isomaltulose synthase) gene from Enterobacter sp. FMB-1

Aims:  Isomaltulose (palatinose) is a slowly digestible sucrose isomer that can reduce both the glycemic and insulinemic response to foods. The aim of this study was to clone and express a sucrose isomerase (SIase) gene and characterize the protein that is responsible for the production of isomaltulose in the micro-organism Enterobacter sp. FMB-1.
Methods and Results:  A cosmid clone containing c. 6 kbp region encoding an SIase gene was identified. The 5969-bp chromosomal DNA fragment covering the SIase ( esi ) gene in Enterobacter sp. FMB-1 was sequenced. Although this DNA fragment contained several open reading frames other than esi , only the presence of esi was sufficient to produce isomaltulose in recombinant Escherichia coli . The esi gene was expressed in E. coli , leading to the characterization of its SIase activity.
Conclusions:  The Enterobacter sp. FMB-1 esi gene was successfully cloned and expressed in E. coli . This gene encoded a functional SIase that produced isomaltulose from sucrose.
Significance and Impact of the Study:  This is the first molecular analysis of an SIase gene in an Enterobacter strain. The functional expression of the Enterobacter sp. FMB-1 esi gene in E. coli offers an alternative choice for the industrial production of isomaltulose.     

Quantitative analysis of histidine decarboxylase gene (hdcA) transcription and histamine production by Streptococcus thermophilus PRI60 under conditions relevant to cheese making

This study evaluated the influence of parameters relevant for cheese making on histamine formation by Streptococcus thermophilus. Strains possessing a histidine decarboxylase (hdcA) gene represented 6% of the dairy isolates screened. The most histaminogenic, S. thermophilus PRI60, exhibited in skim milk a high basal level of expression of hdcA, upregulation in the presence of free histidine and salt, and repression after thermization. HdcA activity persisted in cell extracts, indicating that histamine might accumulate after cell lysis in cheese.     

Histidine decarboxylases and their role in accumulation of histamine in tuna and dried saury

Histamine-producing bacteria (HPB) such as Photobacterium phosphoreum and Raoultella planticola possess histidine decarboxylase (HDC), which converts histidine into histamine. Histamine fish poisoning (HFP) is attributable to the ingestion of fish containing high levels of histamine produced by HPB. Because freezing greatly decreases the histamine-producing ability of HPB, especially of P. phosphoreum, it has been speculated that HFP is caused by HDC itself from HPB cells autolyzing during frozen storage, even when HPB survive frozen storage. Here we constructed recombinant HDCs of P. phosphoreum, Photobacterium damselae, R. planticola, and Morganella morganii and investigated the ability of HDCs to produce sufficient histamine to cause HFP. To elucidate the character of these HDCs, we examined the specific activity of each recombinant HDC at various temperatures, pH levels, and NaCl concentrations. Further, we also investigated the stability of each HDC under different conditions (in reaction buffer, tuna, and dried saury) at various temperatures. P. damselae HDC readily produced sufficient histamine to cause HFP in fish samples. We consider that if HDC is implicated as an independent cause of HFP in frozen-thawed fish, the most likely causative agent is HDC of P. damselae.     

Regulation of hdc expression and HDC activity by enological factors in lactic acid bacteria

Aims: The aim of this work was to study the influence of enological factors on the histidine decarboxylase gene (hdc) expression and on histidine decarboxylase enzyme (HDC) activity in Lactobacillus hilgardii, Pediococcus parvulus and Oenococcus oeni. Methods and Results: Cell extracts and whole cells were used. Glucose, fructose, malic acid and citric acid diminished the hdc expression. Ethanol did not increase hdc expression or activity in cells, but increased HDC activity. Temperature and pH had effect on the activity of HDC but not on hdc expression. Tartaric acid and l -lactic acid, and sulphur dioxide (SO₂) had no effect on enzyme synthesis and activity. Bacterial species differ in the relative enzymatic activity but all the factors affected similarly to L. hilgardii, P. parvulus and O. oeni. Conclusions: The hdc gene expression was lowered by glucose, fructose, malic acid, and citric acid, whereas ethanol enhanced the HDC enzyme activity. The conditions that normally occur during malolactic fermentation and later on, could favour histamine production. SO₂ could prevent bacterial growth, but does not diminish the HDC enzyme activity. Significance and Impact of the Study: Information on hdc expression and HDC activity can contribute to the prevention of histamine formation during wine production and storage.     

Histidine Decarboxylases and Their Role in Accumulation of Histamine in Tuna and Dried Saury

Histamine-producing bacteria (HPB) such as Photobacterium phosphoreum and Raoultella planticola possess histidine decarboxylase (HDC), which converts histidine into histamine. Histamine fish poisoning (HFP) is attributable to the ingestion of fish containing high levels of histamine produced by HPB. Because freezing greatly decreases the histamine-producing ability of HPB, especially of P. phosphoreum, it has been speculated that HFP is caused by HDC itself from HPB cells autolyzing during frozen storage, even when HPB survive frozen storage. Here we constructed recombinant HDCs of P. phosphoreum, Photobacterium damselae, R. planticola, and Morganella morganii and investigated the ability of HDCs to produce sufficient histamine to cause HFP. To elucidate the character of these HDCs, we examined the specific activity of each recombinant HDC at various temperatures, pH levels, and NaCl concentrations. Further, we also investigated the stability of each HDC under different conditions (in reaction buffer, tuna, and dried saury) at various temperatures. P. damselae HDC readily produced sufficient histamine to cause HFP in fish samples. We consider that if HDC is implicated as an independent cause of HFP in frozen-thawed fish, the most likely causative agent is HDC of P. damselae.     

Histamine H1 and H2 receptors but not H4 receptors are upregulated during bone marrow regeneration

The role of histamine receptors in radiation-induced bone marrow (BM) regeneration was investigated with aspects of functional genomics. H1R and H2R mRNA expression increased during regeneration in both histidine decarboxylase knockout (HDC-/-) and wild type (HDC+/+) mice, though to a lesser extent in HDC-/- mice. H4R mRNA expression was downregulated in both groups. Mainly CD34+ cells were responsible for the elevation of intracellular histamine and HDC content in HDC+/+ BM cell populations. The differential changes in the expression of its receptors, and also its elevated levels in hematopoietic progenitors support the regulatory role of histamine in BM regeneration, that could be further explored by future gene expression studies.     

Augmented lipopolysaccharide-induction of the histamine-forming enzyme in streptozotocin-induced diabetic mice

Disorders of the microcirculation and reduced resistance to infection are major complications in diabetes. Histamine enhances capillary permeability, and may also reduce cellular immunity. Here we demonstrate that streptozotocin (STZ)-induced diabetes in mice not only enhances the activity of the histamine-forming enzyme, histidine decarboxylase (HDC), but also augments the lipopolysaccharide (LPS)-induced elevation of HDC activity in various tissues, resulting in a production of histamine. The augmentation of HDC activity occurred as early as 2 days after STZ injection, but was not seen in nondiabetic mice. When given to STZ-treated mice, nicotinamide, an inhibitor of poly(ADP-ribose) synthetase, reduced both the elevation of blood glucose and the elevations of HDC activity and histamine production. These results suggest that hyperglycemia may initiate a sequence of events leading not only to an enhancement of basal HDC activity, but also to a sensitization of mice to the HDC-inducing action of LPS. We hypothesize that bacterial infections and diabetic complications may mutually exacerbate one another because both involved an induction of HDC.     

Histamine and histidine decarboxylase are hallmark features of ECL cells but not G cells in rat stomach

The oxyntic mucosa of the rat stomach is rich in ECL cells which produce and secrete histamine in response to gastrin. Histamine and the histamine-forming enzyme histidine decarboxylase (HDC) have been claimed to occur also in the gastrin-secreting G cells in the antrum. In the present study, we used a panel of five HDC antisera and one histamine antiserum to investigate whether histamine and HDC are exclusive to the ECL cells. By immunocytochemistry, we could show that the ECL cells were stained with the histamine antiserum and all five HDC antisera. The G cells, however, were not stained with the histamine antiserum, but with three of the five HDC antisera. Thus, histamine and HDC coexist in the ECL cells (oxyntic mucosa) but not in G cells (antral mucosa). Western blot analysis revealed a typical pattern of HDC-immunoreactive bands (74, 63 and 54 kDa) in oxyntic mucosa extracts with all five antisera. In antral extracts, immunoreactive bands were detected with three of the five HDC antisera (same as above); the pattern of immunoreactivity differed from that in oxyntic mucosa. Food intake of fasted rats or treatment with the proton pump inhibitor omeprazole raised the HDC activity and the HDC protein content of the oxyntic mucosa but not of the antral mucosa; the HDC activity in the antrum was barely detectable. We suggest that the HDC-like immunoreactivity in the antrum represents a cross-reaction with non-HDC proteins and conclude that histamine and HDC are hallmark features of ECL cells but not of G cells.     

Effects of histamine and interleukin-4 synthesized in arterial intima on phagocytosis by monocytes/macrophages in relation to atherosclerosis

We investigated the localization of histidine decarboxylase (HDC), which is the rate-limiting enzyme that generates histamine from histidine, in human aorta/coronary artery. RT-PCR and immunohistochemical staining revealed that the HDC gene was expressed in monocytes/macrophages and T cells in the arterial intima but not in smooth muscle cells in either the arterial intima or the media. A luciferase promoter assay with U937 and Jurkat cells demonstrated that interleukin-4 (IL-4) inhibited the expression of the HDC gene. In contrast, among a scavenger receptor family, IL-4 as well as histamine up-regulated U937 cells to express the LOX-1 gene but not the SR-A gene, which genes encode receptors that scavenge oxidized lipids. These findings suggest that histamine synthesized in the arterial wall participates in the initiation and progression of atherosclerosis and that IL-4 can act as an important inhibitory and/or stimulatory factor in the function of monocytes/macrophages modulated by histamine in relation to the process of atherosclerosis.     

Transforming growth factor-alpha directly augments histidine decarboxylase and vesicular monoamine transporter 2 production in rat enterochromaffin-like cells

For the production and vesicle storage of histamine, Enterochromaffin-like (ECL) cells express histidine decarboxylase (HDC) and vesicular monoamine transporter 2 (VMAT2). Although HDC and VMAT2 show dynamic changes during gastric ulcer healing, the control system of their expression has not been fully investigated. In the present study, we investigated the effect of transforming growth factor-alpha (TGF-alpha) and proinflammatory cytokines on HDC and VMAT2 expression in rat ECL cells. Time course changes in the expression of TGF-alpha during the healing of acetic acid-induced ulcers were studied. EGF receptor (EGFR) expression was also examined in ECL cells, whereas the direct effects of TGF-alpha and proinflammatory cytokines on HDC and VMAT2 expression in ECL cells were investigated using in vivo and in vitro models. During the process of ulcer healing, expression of TGF-alpha mRNA was markedly augmented. Furthermore, EGFR was identified in isolated ECL cells. TGF-alpha stimulated HDC and VMAT2 mRNA expression and protein production and also increased histamine release from ECL cells. Selective EGFR tyrosine kinase inhibitor tyrphostin AG1478 almost completely inhibited HDC and VMAT2 gene expression induced by TGF-alpha in vivo and in vitro. During gastric mucosal injury, TGF-alpha was found to stimulate ECL cell functions by increasing HDC and VMAT2 expression.     

Histidine decarboxylase gene expression in rat fundus is regulated by gastrin

The conversion of histidine to histamine by histidine decarboxylase (HDC) is of central importance in the control of vertebrate acid secretion. We have used PCR-generated probes to study the regulation of HDC gene expression in rat fundic mucosa. When circulating gastrin levels were lowered by fasting or elevated by treatment with omeprazole, there were parallel changes in HDC mRNA abundance. However, when animals with elevated gastrin levels were concurrently treated with the gastrin/CCK-B receptor antagonist PD 134308, HDC mRNA levels were not increased. These data are consistent with the hypothesis that HDC gene expression is regulated by gastrin, over the physiological range of circulating hormone concentrations.