Phenylalanine ammonia lyase (PAL) enzyme activity and antioxidant properties of some cyanobacteria isolates

In the present study, six cyanobacteria isolates were evaluated for the PAL enzyme activity, and their methanol extracts were assessed for the total phenolic amount and other antioxidant parameters. Synechocystis sp. BASO444 and Synechocystis sp. BASO673 isolates with high levels of total phenols (66.0 ± 1.2 μg/mg, 78.1 ± 1.8 μg/mg, respectively) also showed high levels of PAL activities (20.5 ± 3.1 U/mg protein, 17.2 ± 2.3 U/mg protein, respectively) and strong antioxidant activities. To understand the effect of l-phenylalanine (l-phe) on the PAL activity, total phenolic amount, and phenolic constituents, isolates were evaluated with 100 mg/l l-phe. While PAL activities exhibited no significant change with l-phe addition, total phenolic amount of the isolates significantly increased. HPLC analysis revealed gallic acid, trans-cinnamic acid, p-coumaric acid, and ferulic acid as the main compounds. Results suggested that the two isolate mights be an important source for the l-phe inducible phenolic compounds.     

乙酰肝素酶Arg307Lys多态性与成年人急性白血病发病风险的关系

目的 探讨乙酰肝素酶( HPSE) Arg307Lys多态性与成年人急性白血病发病风险的关系。方法按照1:1配对病例对照研究方法,选择中国北方地区100例急性髓系白血病(AML)和25例急性淋巴细胞白血病(ALL)患者为病例组,100名中国北方地区健康人为对照组,采用聚合酶链反应-限制性片段长度多态性( PCR-RFLP)方法检测观察对象外周血HPSE Arg307Lys基因多态性。结果成年ALL病例组和对照组Lys/Lys、Arg/Lys、Arg/Arg基因型分布频率分别为80％、16％、4％和75％、23％、2％,两组比较差异无统计学意义(x2= 0.07,P= 0.79; x2= 0,08,P= 0.78)。AML病例组Lys/Lys、Arg/Lys、Arg/Arg基因型频率分别为85％、14％、1％,与对照组比较差异无统计学意义(x2=3.03,P=0.08;x2=3.15,P=0.08)。携带HPSE Arg307Lys突变基因(AA/AA+AG)的个体不增加AML及ALL的发病风险(AML:x2= 3.13,P=0.07,OR= 1.89,95％CI 0.93～3.83;AL：x 2=0.27,P=0.60,OR= 1.33,95 ％CI 0.45～ 3.90)。结论HPSE Arg307Lys与中国北方地区急性白血病的发生可能无关。     

Molecular identification and pectate lyase production by Bacillus strains involved in cocoa fermentation

We have previously reported the implication of Bacillus in the production of pectinolytic enzymes during cocoa fermentation. The objective of this work was to identify the Bacillus strains isolated from cocoa fermentation and study their ability to produce pectate lyase (PL) in various growth conditions. Ninety-eight strains were analyzed by Amplified Ribosomal DNA Restriction Analysis (ARDRA). Four different banding patterns were obtained leading to the clustering of the bacterial isolates into 4 distinct ARDRA groups. A subset of representative isolates for each group was identified by 16S rRNA gene partial sequencing. Six species were identified: Bacillus subtilis, Bacillus pumilus, Bacillus sphaericus, Bacillus cereus, Bacillus thuringiensis, together with Bacillus fusiformis which was isolated for the first time from cocoa fermentation. The best PL producers, yielding at least 9 U/mg of bacterial dry weight, belonged to B. fusiformis, B. subtilis, and B. pumilus species while those belonging to B. sphaericus, B. cereus and B. thuringiensis generally showed a low level of activity. Two kinds of PL were produced, as revealed by isoelectrofocusing: one with a pI of 9.8 produced by B. subtilis and B. fusiformis, the other with a pI of 10.5 was produced by B. pumilus. Strains yielded about 2 fold more PL in a pectic compound medium than in glucose medium and maximum enzyme production occurred in the late stationary bacterial growth phase. Together all these results indicate that PL production in the bacilli studied is modulated by the growth phase and by the carbon source present in the medium.     

噬菌体裂解酶在食品安全领域的研究进展

食源性疾病引发的食品安全问题对人类健康造成严重危害, 其中微生物致病菌是引起食源性疾病的最主要因素,近年来国内外由微生物致病菌引起的食源性疾病事件频频发生,受到世界各国的高度关注。食品工业防治食源性致病微生物的传统方法中,化学防腐剂存在副作用、天然防腐剂较弱的抗微生物活性以及大规模抗生素使用带来的耐药性等一系列问题,使寻求新的抗菌药物或制剂迫在眉睫。噬菌体裂解酶是双链DNA噬菌体复制后期表达, 能够裂解细菌细胞壁释放子代噬菌体的一种蛋白水解酶。随着近些年针对噬菌体及其产物展开的研究不断深入,噬菌体裂解酶凭借高度特异性、不影响正常菌群等特性, 从治疗人类耐药感染到控制多个领域的细菌污染, 成为了包括微生物食品安全在内多种应用中有效的抗微生物制剂。     

红熟期番茄果实根霉果腐病与相关酶活性变化的研究

以"中蔬4号"红熟期番茄果实为材料,采用损伤接种的方法对番茄果实进行处理,测定其苯丙氨酸解胺酶(PAL)和几丁质酶(CHT)活性,研究这2种酶与番茄对根霉果腐病抗性的关系。结果表明,果腐根霉的侵染能够显著提高红熟期番茄果实PAL和CHT的活性,呈现出各自不同的变化趋势。     

褐藻胶裂解酶基因在大肠杆菌中的表达及其酶学性质

作者从蜡样芽孢杆菌F1-5-10中提取DNA,通过PCR克隆得到褐藻胶裂解酶基因后,将其构建到pET-30a(+)上并在大肠杆菌BL21菌株中进行高效诱导表达,继而对纯化得到的褐藻胶裂解酶蛋白进行活性检测和酶学特性研究。实验结果表明:PCR扩增出1035bp大小的褐藻胶裂解酶基因algl(GenBank登录号:GU585575),SDS-PAGE电泳结果显示出相对分子质量约为45 000的特异性蛋白质条带。表达条件优化实验结果表明0.4mmol/L浓度的IPTG 32℃诱导4h重组蛋白的表达量最高,约占菌体总蛋白质质量的36%。测定褐藻胶裂解酶酶活性,酶活力为11.7U/mg。酶学性质研究表明:ALGL的酶活最适温度为35℃,热稳定性较差,最适pH值为6.6,Ca2+、Mg2对酶活有激活作用,ALGL催化褐藻胶的Km值为1.89mg/mL,Vmax为15.01U/mL。     

Volatile compounds and changes in flavour‐related enzymes during cold storage of high‐intensity pulsed electric field‐ and heat‐processed tomato juices

BACKGROUND: The effects of high‐intensity pulsed electric field (HIPEF) processing (35 kV cm^?1 for 1500 µs, using 4 µs bipolar pulses at 100 Hz) on the production of volatile compounds and flavour‐related enzymes in tomato juice were investigated and compared with those of thermal processing (90 °C for 30 or 60 s). RESULTS: Tomato juice treated by HIPEF showed lower residual lipoxygenase (LOX) activity (70.2%) than juice heated at 90 °C for 60 s (80.1%) or 30 s (93.2%). In contrast, hydroperoxide lyase (HPL) was almost completely inactivated when the juice was subjected to 90 °C for 60 s, whereas roughly 50% of the control tomato juice was depleted after HIPEF treatment or thermal processing at 90 °C for 30 s. A slight decrease was observed in the initial LOX activity of treated and untreated samples during storage, whereas initial HPL activity was strongly affected over time. CONCLUSION: HIPEF‐treated juice exhibited higher levels of compounds contributing to tomato aroma than untreated and heat‐treated juices throughout storage. Thus HIPEF processing can preserve flavour quality and stability of tomato juice compared with conventional thermal treatments. Copyright © 2010 Society of Chemical Industry     

一株碱性果胶酶高产菌株的筛选与鉴定

对天津盐碱地土壤样品中分离筛选的碱性果胶酶高产菌株进行生理生化及分子生物学鉴定,确定其生物学分类地位。以果胶为底物从土壤中筛选碱性果胶酶生产菌株,对复筛获得的菌株L520进行16SrDNA基因测序和分析,结合Biolog微生物鉴定系统完成L520的菌种鉴定;常规的生理生化反应鉴定进一步阐明该菌株的生理生化特性。菌株L520在LB培养基上培养10 h左右产中生芽孢,能利用葡萄糖、甘露醇、木糖为碳源进行生长,降解淀粉,水解酪蛋白但不水解酪氨酸;16SrDNA（NCBI登陆号FJ906822）结果显示该菌株与枯草芽孢杆菌、地衣芽孢杆菌等有99%的相似性,Biolog鉴定系统中菌株L520培养16~24 h与Bacillus subtilis A相关数据为PROB 99%,SIM 0.853,DIST 2.06。该碱性果胶酶高产菌株分类学上属于芽孢杆菌属的枯草芽孢杆菌,命名为Bacillus subtilis L520,碱性果胶酶发酵活性达到45 U/mL。