Beneficial Lactic Acid Bacteria
K. Balamurugan, U. Prithika in Pocket Guide to Bacterial Infections, 2019
LAB are producers of many ferments that can be used in various fields. Enzymes degrade caseins yielding key flavor components, which contribute to the sensory perception of dairy products (Smit et al. 2005). These bacteria also possess a broad array of enzymatic activities influencing wine composition and quality of wine (Matthews et al. 2004). Some representatives of genera Lactobacillus, Lactococcus, and Streptococcus demonstrated amylolytic activity. It provides opportunity to produce lactic acid directly from starch as a carbon source (Petrova et al. 2013). β-galactosidase, or lactase, is extensively used in food and pharmaceutical industries due to its capability to hydrolyze lactose to monosaccharide and eliminate lactose intolerance problem (de Vrese et al. 2001).
Macromolecular Absorption From The Digestive Tract In Young Vertebrates
Károly Baintner in Intestinal Absorption of Macromolecules and Immune Transmission from Mother to Young, 2019
Di- and trisaccharides of the milk have to be split by enzymes to monosaccharides, for only the latter can be absorbed by carrier proteins of the brush border. An enzyme that splits lactose resides on the outer surface of the brush-border membrane in the form of small knobs, and has lactase, β-galactosidase, β-glucosidase, and cellobiase activities. It is found primarily on the proximal part of the intestine, where the pH does not much differ from its optimum at pH 5.0 to 5.5. It is called lactase or “neutral” β-galactosidase because its pH optimum is less acidic than that of the lysosomal type “acid” β-galactosidase (pH 3.0 to 4.0). The latter enzyme is found primarily in the vacuolated part of the intestine, probably dissolved in the vacuoles. It splits hetero^-galactosides more rapidly than lactose. A third β-galactosidase is found dissolved in the cytoplasm of enterocytes; it is the “hetero-β-galactosidase” with neutral pH-optimum, without any activity towards lactose. During closure, activity of acid β-galactosidase dramatically declines, while the decrease of lactase activity needs much more time.736
Molecular Recognition and Chemical Modification of Biopolymers — Two Main Components of Affinity Modification
Dmitri G. Knorre, Valentin V. Vlassov in Affinity Modification of Biopolymers, 1989
Although the beginning of RNA synthesis does not necessarily mean that it will be safely finished, this step is crucial for the production of new RNA molecules. The region of template DNA recognized by RNA polymerase prior to initiation is called the promoter. In prokaryotes one promoter often precedes several functionally related genes. For example, there exists a special lac promoter which governs the transcription of several genes coding for proteins necessary for the utilization of lactose. Among them, lactose permease participates in the transfer of lactose and other galactosides via the cell membrane and β-galactosidase catalyzes the hydrolysis of lactose and other β-galactosides. Another well-studied promoter is the trp promoter governing the transcription of five genes coding for enzymes participating in the conversion of anthranilic acid to tryptophane.
Coordinated interaction between Lon protease and catalase-peroxidase regulates virulence and oxidative stress management during Salmonellosis
Published in Gut Microbes, 2022
Perumalraja Kirthika, Vijayakumar Jawalagatti, Amal Senevirathne, John Hwa Lee
The Lon proteolytic domain (Lon PD) contains a conserved lysine (Lys722), located 43 residues beyond the catalytic serine (Ser679) to carry out catalytic activities.26 To understand how Lon protease is involved in the degradation of KatG, we investigated whether KatG physically interacts with the proteolytic active site of Lon protease. We used a bacterial two-hybrid assay to assess the interaction between KatG and the PD of Lon protease by expressing the katG gene with a C-terminal fusion of the cyaA-T18 fragment and lon PD genes with N-terminal fusions of the cyaA-T25 fragment in an E. coli strain lacking CyaA adenylate cyclase. We then spotted cells on a MacConkey agar plate containing maltose and measured β-galactosidase production from a cAMP-dependent promoter produced when T18 and T25 fragments of the cyaA gene are functionally complemented by a physical interaction between fused KatG and the PD of Lon protease. The strain expressing KatG-T18 and the T25-Lon proteolytic domain showed a strong red color on the MacConkey-maltose plate, indicating that KatG interacts with Lon PD (Figure 3a). By contrast, no interaction was observed in KatG-T18 co-expressing the empty T25 fragment. The interaction was confirmed by measuring the β-galactosidase activity. The KatG-Lon PD interaction was further analyzed by in vitro cross-linking of purified proteins. We observed an additional band corresponding to roughly 99 kDa (79 + 20) on polyacrylamide gel when KatG and the Lon proteolytic domain were incubated with a cross-linker (Figure 3a).
Enzyme-assisted modification of flavonoids from Matricaria chamomilla: antioxidant activity and inhibitory effect on digestive enzymes
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2020
Elida Paula Dini de Franco, Fabiano Jares Contesini, Bianca Lima da Silva, Anna Maria Alves de Piloto Fernandes, Camila Wielewski Leme, João Pedro Gonçalves Cirino, Paula Renata Bueno Campos, Patrícia de Oliveira Carvalho
The bioconversion reaction was carried out in screw-capped glass tubes with shaking (130 rpm) at controlled temperature (40 °C) for 8 h using 10 ml of aqueous infusion of Matricaria chamomilla. To initiate the hydrolysis of the flavonoid glycosides, 1 ml of enzyme mixture solution prepared in 0.1 M acetate buffer pH 4.0 was added to the reaction mixture. The enzyme mixture used had equal parts of each up (hesperidinase and β-galactosidase) to a final concentration of 0.02 mg/mL. Optimisation of hydrolysis conditions and incubation time using the enzyme combination was previously performed21. The reactions were stopped by boiling for 20 min and the samples were stored in a refrigerator to await analysis. The assays were performed in triplicate. According to the manufacturer’s information, hesperidinase expresses both α-l-rhamnosidase (EC 3.2.1.40) and β-d-glucosidase (3.2.1.21) activities. One unit will liberate 1.0 µmole of reducing sugar (as glucose) from hesperidin per min at pH 3.8, at 40 °C. For β-galactosidase activity, one unit will hydrolyse 1.0 µmole of lactose per minute at pH 4.5, at 30 °C.
A putative LysR-type transcriptional regulator inhibits biofilm synthesis in Pseudomonas aeruginosa
Published in Biofouling, 2019
Xiaojing Yang, Zhiqiang Zhang, Zhiwei Huang, Xixi Zhang, Donghang Li, Li Sun, Jiajia You, Xuewei Pan, Hongjiang Yang
The crystal violet staining method was used in measuring biofilm amounts of the indicated P. aeruginosa strains as described previously (Djordjevic et al. 2002). In brief, a Corning 96-well microtiter plate (Corning, NY, USA) was used in the assays. Bacteria were incubated in three-fold diluted LB medium at 37 °C for 48 h. Cultures were collected for measurement of β-galactosidase activity. The microplates were washed gently with distilled water three times. Biofilm was stained with 190: 1% crystal violet solution for 15 min. Ethanol was used to extract the crystal violet and to measure the optical densities at the wavelength 595 nm by using an Infinite F50 ELISA plate reader (Tecan, Switzerland). Triplicates of each sample were tested and the Student’s t-test was performed to analyze the differences.
Related Knowledge Centers
- Catalysis
- Enzyme
- Exoglycosidase
- Galactose
- Ganglioside
- Glycosidic Bond
- Glycoprotein
- Glycoside Hydrolase
- Substrate
- Lactose