Molecular characterization of bile salt hydrolase from Bifidobacterium animalis subsp. lactis Bi30

The present work describes the identification, purification, and characterization of bile salt hydrolase (BSH) from Bifidobacterium animalis subsp. lactis. The enzyme was purified to electrophoretic homogeneity by hydrophobic chromatography, ion-exchange chromatography and ultrafiltration. SDS-PAGE analysis of putative BSH and gel filtration revealed that the analyzed protein is presumably a tetramer composed of four monomers each of about 35 kDa. The purified enzyme was analyzed by liquid chromatography coupled to LTQ FT ICR mass spectrometry and unambiguously identified as a bile salt hydrolase from B. animalis. The isoelectric point of the studied protein was estimated to be around pH 4.9. The pH optimum of the purified BSH is between 4.7 to 6.5, and the temperature optimum is around 50 degrees C. The BSH of B. animalis could deconjugate all tested bile salts, with clear preference for glycine-conjugated bile salts over taurine-conjugated forms. Genetic analysis of the bsh showed high similarity to the previously sequenced bsh gene from B. animalis and confirmed the usefulness of bile salt hydrolase as a genetic marker for B. animalis identification.     

Molecular cloning, characterization and heterologous expression of bile salt hydrolase (Bsh) from Lactobacillus fermentum NCDO394

Bile salt hydrolase (Bsh) active probiotic strains hydrolyze bile acid amino conjugates in vivo, which triggers cholesterol consumption in liver to synthesize new bile leading to consequential cholesterol lowering. Hence, bile salt hydrolyzing potential was the criterion to select L. fermentum NCDO394 for this study and its gene encoding Bsh was identified and cloned. The resulting nucleotide sequence of bsh gene contained an open reading frame (ORF) of 978 nucleotides encoding a predicted protein of 325 amino acids with a theoretical pI of 6.39. Moreover, deduced Bsh protein had high similarity with the Bshs of L. fermentum only and also exhibited significant similarity to the Pencillin V amidases of other Lactobacillus spp. Five catalytically important amino acids were highly conserved in L. fermentum Bsh while four amino acid motifs around these active sites, were not as consistent as in other Bsh proteins. Furthermore, L. fermentum bsh gene was sub-cloned into pET-28b(+) vector, and its expression was induced with 0.05 mM isopropylthiogalactopyranoside (IPTG) in Escherichia coli BL21(DE3). The recombinant Bsh (rBsh) was purified with homogeneity using Ni⁺²-NTA column and characterized for substrate specificity, pH and temperature. The rBsh hydrolyzed six major human bile salts with a slight preference towards glycine-conjugated bile salts. The optimum pH of rBsh was six, and its enzymatic activity declined below pH 5 and above pH 7. The enzyme was stable and functional even at 65 °C while showed its maximum activity at 37 °C. In conclusion, L. fermentum NCDO394 may be a promising candidate probiotic which may affect cholesterol metabolism in vivo.     

Molecular cloning,characterization and comparison of bile salt hydrolases from Lactobacillus johnsonii PF01

Aims

To clone, characterize and compare the bile salt hydrolase (BSH) genes of Lactobacillus johnsonii PF01.

Methods and Results

The BSH genes were amplified by polymerase chain reaction (PCR) using specific oligonucleotide primers, and the products were inserted into the pET21b expression vector. Escherichia coli BLR (DE3) cells were transformed with pET21b vectors containing the BSH genes and induced using 0·1 mmol l^?1 isopropylthiolgalactopyranoside. The overexpressed BSH enzymes were purified using a nickel–nitrilotriacetic acid (Ni²⁺‐NTA) agarose column and their activities characterized. BSH A hydrolysed tauro‐conjugated bile salts optimally at pH 5·0 and 55°C, whereas BSH C hydrolysed glyco‐conjugated bile salts optimally at pH 5·0 and 70°C. The enzymes had no preferential activities towards a specific cholyl moiety.

Conclusions

BSH enzymes vary in their substrate specificities and characteristics to broaden its activity. Despite the lack of conservation in their putative substrate‐binding sites, these remain functional through motif conservation.

Significance and Impact of the Study

This is to our knowledge the first report of isolation of BSH enzymes from a single strain, showing hydrolase activity towards either glyco‐conjugated or tauro‐conjugated bile salts. Future structural homology studies and site‐directed mutagenesis of sites associated with substrate specificity may elucidate specificities of BSH enzymes.     

唾液乳杆菌BSH1及其突变体的底物特异性

为了解析胆盐水解酶催化中心中关键氨基酸位点与其底物特异性的关系,以大肠杆菌pET-20b(+)表达系统为分子改造平台,采用理性设计,结合氨基酸定点突变的方法,成功构建了唾液乳杆菌Lactobacillus salivarius胆盐水解酶BSH1的7种突变体。通过对比L.salivarius BSH1及其突变体对6种结合胆盐的底物特异性表明,7种突变体对不同的结合胆盐的水解活性有所改变。结果说明,Cys2和Thr264分别是BSH1催化TCA和GCA的关键残基,且对酶的催化活性的保持具有关键作用。其中,高保守性的氨基酸位点Cys2不是BSH1唯一的活性位点,而其他突变的氨基酸位点可能作为BSH1的结合位点参与了底物的结合,也可能影响了底物进入BSH1活性中心的通道或底物结合口袋的体积与形状,进而影响了BSH1对不同结合胆盐的水解活性。     

鸡源和猪源乳杆菌胆盐水解酶的表达及酶学性质比较

【目的】随着抗生素生长促进剂(AGPs)在动物饲料中逐步禁止使用,AGPs替代物的研究成为热点。由于胆盐水解酶(BSH)在脂类代谢中的关键作用,成为AGPs替代物研究的一个重要方向。在原核表达和纯化的基础上鉴定鸡源和猪源乳杆菌BSH在酶学性质方面的差异性。【方法】分别对鸡源胆盐水解酶(BSHc)和猪源胆盐水解酶(BSHp)基因进行原核表达和蛋白纯化,通过测定对6种甘氨结合胆盐和牛磺结合胆盐的水解效率获得两种酶的酶学动力学性质,进而测定了温度、pH和金属离子对酶活力的影响。【结果】BSHc和BSHp对甘氨结合胆盐的水解效率高于牛磺结合胆盐,BSHc对甘氨结合胆盐的水解效率较BSHp稍高;BSHc和BSHp的最适酶解温度分别为45°C和42°C;BSHc和BSHp的最适反应pH分别为6.0和5.4;含有Cu~(2+)、Fe~(3+)、Mn~(2+)和Zn~(2+)的金属盐对BSHc和BSHp的酶活力均具有不同程度的抑制作用,特别是Cu~(2+)和Fe~(3+)抑制作用比较强;含有Na~+、K~+、Mg~(2+)和Ca2+的金属盐对BSHc和BSHp酶活力的抑制作用相对较弱或无抑制作用,但KIO3对BSHc和BSHp酶活力具有强抑制作用,KI和CaCl_2对BSHp酶活力也具有较强的抑制作用。【结论】原核表达和纯化的BSHc和BSHp对甘氨结合胆盐的水解效率高于牛磺结合胆盐,BSHc的最适酶解温度和pH稍高于BSHp,Cu~(2+)、Fe~(3+)、Mn~(2+)和Zn~(2+)等金属离子对BSHc和BSHp酶活力具有明显抑制作用,试验结果为鉴定BSH抑制物进而研制AGPs替代物奠定了基础。     

Cloning and characterization of thermostable endoglucanase (Cel8Y) from the hyperthermophilic Aquifex aeolicus VF5

Aquifex aeolicus is the hyperthermophilic bacterium known, with growth-temperature maxima near 95 degrees C. The cel8Y gene, encoding a thermostable endoglucanase (Cel8Y) from Aquifex aeolicus VF5, was cloned into a vector for expression and expressed in Escherichia coli XL1-Blue. A clone of 1.7 kb fragment containing endoglucanase activity, designated pKYCY100, was sequenced and found to contain an ORF of 978 bp encoding a protein of 325 amino acid residues, with a calculated molecular mass of 38,831 Da. This endoglucanase was designated cel8Y gene. The endoglucanase has an 18-amino-acid signal peptide but not cellulose-binding domain. The endoglucanase of A. aeolicus VF5 had significant amino acid sequence similarities with endoglucanases from glycosyl hydrolase family 8. The predicted amino acid sequence of the Cel8Y protein was similar to that of CMCase of Cellulomonas uda, BcsC of Escherichia coli, CelY of Erwinia chrysanthemi, and CMCase of Acetobacter xylinum. The molecular mass of Cel8Y was calculated to be 36,750 Da, which is consistent with the value obtained from result of CMC-SDS-PAGE of the purified enzyme. Cel8Y was thermostable, exhibiting maximal activity at 80 degrees C and pH optima of 7.0 and with half-lives of 2 h at 100 degrees C, 4 h at 90 degrees C.     

Coexpression of bile salt hydrolase gene and catalase gene remarkably improves oxidative stress and bile salt resistance in <Emphasis Type="Italic">Lactobacillus casei</Emphasis>

Lactic acid bacteria (LAB) encounter various types of stress during industrial processes and gastrointestinal transit. Catalase (CAT) and bile salt hydrolase (BSH) can protect bacteria from oxidative stress or damage caused by bile salts by decomposing hydrogen peroxide (H₂O₂) or deconjugating the bile salts, respectively. Lactobacillus casei is a valuable probiotic strain and is often deficient in both CAT and BSH. In order to improve the resistance of L. casei to both oxidative and bile salts stress, the catalase gene katA from L. sakei and the bile salt hydrolase gene bsh1 from L. plantarum were coexpressed in L. casei HX01. The enzyme activities of CAT and BSH were 2.41 μmol H₂O₂/min/10⁸ colony-forming units (CFU) and 2.11 μmol glycine/min/ml in the recombinant L. casei CB, respectively. After incubation with 8 mM H₂O₂, survival ratio of L. casei CB was 40-fold higher than that of L. casei CK. Treatment of L. casei CB with various concentrations of sodium glycodeoxycholate (GDCA) showed that ~10⁵ CFU/ml cells survived after incubation with 0.5% GDCA, whereas almost all the L. casei CK cells were killed when treaded with 0.4% GDCA. These results indicate that the coexpression of CAT and BSH confers high-level resistance to both oxidative and bile salts stress conditions in L. casei HX01.     

Relationship between bile salt hydrolase activity, changes in the internal pH and tolerance to bile acids in lactic acid bacteria

The effect of the conjugated bile acid (BA) on the microbial internal pH (pHin) values in lactic acid bacteria with and without ability to hydrolyze bile salts (BSH[+] and BSH[-] strains, respectively) was evaluated. BSH(+) strains showed a gradual increase in the pHin following the addition of conjugated BA; this behavior was more pronounced with GDCA than with TDCA may be due to the higher affinity of BSH for the glyco-conjugates acids. Conversely, the BSH(-) strains showed a decrease in internal pH probably as a consequence of weak acid accumulation. As expected, a decrease in the cytoplasmatic pH affected the cell survival in this last group of strains, while the BSH(+) strains were more resistant to the toxic effect of BA. PURPOSE OF WORK: To evaluate bile salt hydrolase activities, changes in the internal pH and cell survival to bile acids in lactic acid bacteria to establish the relationship between these parameters.     

Identification and Characterization of a Bile Salt Hydrolase from Lactobacillus salivarius for Development of Novel Alternatives to Antibiotic Growth Promoters

Antibiotic growth promoters (AGPs) have been used as feed additives to improve average body weight gain and feed efficiency in food animals for more than 5 decades. However, there is a worldwide trend to limit AGP use to protect food safety and public health, which raises an urgent need to discover effective alternatives to AGPs. The growth-promoting effect of AGPs has been shown to be highly correlated with the decreased activity of intestinal bile salt hydrolase (BSH), an enzyme that is produced by various gut microflora and involved in host lipid metabolism. Thus, BSH inhibitors are likely promising feed additives to AGPs to improve animal growth performance. In this study, the genome of Lactobacillus salivarius NRRL B-30514, a BSH-producing strain isolated from chicken, was sequenced by a 454 GS FLX sequencer. A BSH gene identified by genome analysis was cloned and expressed in an Escherichia coli expression system for enzymatic analyses. The BSH displayed efficient hydrolysis activity for both glycoconjugated and tauroconjugated bile salts, with slightly higher catalytic efficiencies (k_cat/K_m) on glycoconjugated bile salts. The optimal pH and temperature for the BSH activity were 5.5 and 41°C, respectively. Examination of a panel of dietary compounds using the purified BSH identified some potent BSH inhibitors, in which copper and zinc have been recently demonstrated to promote feed digestion and body weight gain in different food animals. In sum, this study identified and characterized a BSH with broad substrate specificity from a chicken L. salivarius strain and established a solid platform for us to discover novel BSH inhibitors, the promising feed additives to replace AGPs for enhancing the productivity and sustainability of food animals.     

植物乳杆菌JPP2胆盐水解酶相关基因克隆和表达

通过PCR方法从植物乳杆菌JPP2中扩增出胆盐水解酶（BSH）相关基因bsh3,利用中间克隆载体pMD19-T将其构建于表达载体pET-28b上,并转化入表达宿主菌E．coli BL21（DE3）,成功构建重组BSH的工程菌。核苷酸及推导的氨基酸序列分析表明,正确克隆出目的基因。诱导表达后,SDS-PAGE电泳结果显示出特异性蛋白质条带,其分子量约为38kDa。此单克隆体系的构建为进一步研究BSH的功能奠定基础。     

Cloning and functional expression of an alpha-galactosidase from Yersinia pestis biovar Microtus str. 91001

A gene encoding a glycoside hydrolase (GH) family 36 alpha-galactosidase was cloned from Yersinia pestis biovar Microtus str. 91001 and expressed in Escherichia coli. The purified recombinant alpha-galactosidase (Aga-Y) was optimally active at 37 degrees C and pH 6.8. The features of temperature profile, thermoliability, kinetics, and amino acid composition indicated that Aga-Y had properties of a cold-adapted enzyme.     

mCherry红色荧光标记乳酸菌的融合表达系统构建及应用

为开发新型荧光蛋白标记乳酸菌以填补国内研究空白,利用pSIP载体,构建了以红色荧光蛋白mCherry为标记,并以乳酸菌胆盐水解酶基因bsh为报告基因的乳酸菌融合表达系统。在4种不同启动子(P_(sppA)、P_(ldhL)、P_(32)和P_(slpA))调节下,相继实现了融合基因的诱导型和组成型表达,表达的融合重组蛋白mCherry-BSH同时检测出红色荧光活性和胆盐水解酶BSH活性。mCherry红色荧光标记的乳酸菌融合表达系统的成功构建不仅为研究乳酸菌在生物体内的分布、定植及存活情况从而揭示其益生功能的作用机理提供有利条件,也为更多活性蛋白在乳酸菌宿主中的表达、细胞定位、功能鉴定的研究奠定基础。     

Purification and Characterization of Conjugated Bile Salt Hydrolase from Bifidobacterium longum BB536

Bifidobacterium species deconjugate taurocholic, taurodeoxycholic, taurochenodeoxycholic, glycocholic, glycodeoxycholic, and glycochenodeoxycholic acids. The enzyme level increases in the growth phase. No increase in activity is observed for the cytoplasmic enzyme after addition of conjugated bile acids to a stationary-phase culture. Conjugated bile salt hydrolase (BSH) was purified from Bifidobacterium longum BB536. Its apparent molecular mass in denaturing polyacrylamide gel electrophoresis was ca. 40,000 Da. The intact enzyme had a relative molecular weight of ca. 250,000 as determined by gel filtration chromatography, suggesting that the native BSH of B. longum is probably a hexamer. The purified enzyme is active towards both glycine and taurine conjugates of cholate, deoxycholate, and chenodeoxycholate. The pH optimum is in the range of 5.5 to 6.5. A loss of BSH activity is observed after incubation at temperatures higher than 42(deg)C; at 60(deg)C, 50% of the BSH activity is lost. The importance of free sulfhydryl groups at the enzyme active center is suggested. For B. longum BB536, no significant difference in the initial rate of deconjugation and enzymatic efficiency appears between bile salts. The enzymatic efficiency is higher for B. longum BB536 than for other genera. In this paper, a new method which permits a display of BSH activity directly on polyacrylamide gels is described; this method confirms the molecular weight obtained for B. longum BB536 BSH.     

Cloning and expression of a conjugated bile acid hydrolase gene from Lactobacillus plantarum by using a direct plate assay.

The conjugated bile acid hydrolase gene from the silage isolate Lactobacillus plantarum 80 was cloned and expressed in Escherichia coli MC1061. For the screening of this hydrolase gene within the gene bank, a direct plate assay developed by Dashkevicz and Feighner (M. P. Dashkevicz and S. D. Feighner, Appl. Environ. Microbiol. 53:331-336, 1989) was adapted to the growth requirements of E. coli. Because of hydrolysis and medium acidification, hydrolase-active colonies were surrounded with big halos of precipitated, free bile acids. This phenomenon was also obtained when the gene was cloned into a multicopy shuttle vector and subsequently reintroduced into the parental Lactobacillus strain. The cbh gene and surrounding regions were characterized by nucleotide sequence analysis. The deduced amino acid sequence was shown to have 52% similarity with a penicillin V amidase from Bacillus sphaericus. Preliminary characterization of the gene product showed that it is a cholylglycine hydrolase (EC 3.5.1.24) with only slight activity against taurine conjugates. The optimum pH was between 4.7 and 5.5. Optimum temperature ranged from 30 to 45 degrees C. Southern blot analysis indicated that the cloned gene has similarity with genomic DNA of bile acid hydrolase-active Lactobacillus spp. of intestinal origin.     

Cloning and expression of a conjugated bile acid hydrolase gene from Lactobacillus plantarum by using a direct plate assay.

The conjugated bile acid hydrolase gene from the silage isolate Lactobacillus plantarum 80 was cloned and expressed in Escherichia coli MC1061. For the screening of this hydrolase gene within the gene bank, a direct plate assay developed by Dashkevicz and Feighner (M. P. Dashkevicz and S. D. Feighner, Appl. Environ. Microbiol. 53:331-336, 1989) was adapted to the growth requirements of E. coli. Because of hydrolysis and medium acidification, hydrolase-active colonies were surrounded with big halos of precipitated, free bile acids. This phenomenon was also obtained when the gene was cloned into a multicopy shuttle vector and subsequently reintroduced into the parental Lactobacillus strain. The cbh gene and surrounding regions were characterized by nucleotide sequence analysis. The deduced amino acid sequence was shown to have 52% similarity with a penicillin V amidase from Bacillus sphaericus. Preliminary characterization of the gene product showed that it is a cholylglycine hydrolase (EC 3.5.1.24) with only slight activity against taurine conjugates. The optimum pH was between 4.7 and 5.5. Optimum temperature ranged from 30 to 45 degrees C. Southern blot analysis indicated that the cloned gene has similarity with genomic DNA of bile acid hydrolase-active Lactobacillus spp. of intestinal origin.     

Functional Analysis of Four Bile Salt Hydrolase and Penicillin Acylase Family Members in Lactobacillus plantarum WCFS1

Bile salts play an important role in the digestion of lipids in vertebrates and are synthesized and conjugated to either glycine or taurine in the liver. Following secretion of bile salts into the small intestine, intestinal microbes are capable of deconjugating the glycine or taurine from the bile salts, using an enzyme called bile salt hydrolase (Bsh). Intestinal lactobacilli are regarded as major contributors to bile salt hydrolysis in vivo. Since the bile salt-hydrolyzing strain Lactobacillus plantarum WCFS1 was predicted to carry four bsh genes (bsh1, bsh2, bsh3, and bsh4), the functionality of these bsh genes was explored using Lactococcus lactis heterologous overexpression and multiple bsh deletion strains. Thus, Bsh1 was shown to be responsible for the majority of Bsh activity in L. plantarum WCFS1. In addition, bsh1 of L. plantarum WCFS1 was shown to be involved in conferring tolerance to specific bile salts (i.e., glycocholic acid). Northern blot analysis established that bsh1, bsh2, bsh3, and bsh4 are all expressed in L. plantarum WCFS1 during the exponential growth phase. Following biodiversity analysis, bsh1 appeared to be the only bsh homologue that was variable among L. plantarum strains; furthermore, the presence of bsh1 correlated with the presence of Bsh activity, suggesting that Bsh1 is commonly responsible for Bsh activity in L. plantarum strains. The fact that bsh2, bsh3, and bsh4 genes appeared to be conserved among L. plantarum strains suggests an important role of these genes in the physiology and lifestyle of the species L. plantarum. Analysis of these additional bsh-like genes in L. plantarum WCFS1 suggests that they might encode penicillin acylase rather than Bsh activity, indicating their implication in the conversion of substrates other than bile acids in the natural habitat.