β-lactoglobulin peptides obtained by chymotrypsin hydrolysis

Objective: Whey proteins, as β-lactoglobulin, have biological activity. Controlled hydrolysis of this protein could generate peptides with some biological function. The aim of this work was to analyze the peptides resulting from the in vitro hydrolysis with chymotrypsin in order to evaluate the presence of bioactive peptides. Design/methodology/approach: Chymotrypsin was used in the hydrolysis of β-lactoglobulin, and its peptides were evaluated by ultrafiltration, electrophoresis, and mass spectrometry. Findings/conclusion: Results showed that 2 h of chymotrypsin hydrolysis (T1) released peptides with molecular weight values of 8 and 9 KDa, while 4 h of hydrolysis (T2) produced peptides with molecular mass weight values of 7 and 5 KDa. The mass spectrometry (MALDI-TOF) showed six peaks and five of them were comparable with those obtained by in silico hydrolysis results (done previously by Fonseca Ayala, 2018). The identified peptides (DTDYK, DAQSAPL and LKPTPEGDL) in the fraction <1 kDa showed inhibitory activity of angiotensin converting enzyme and inhibitory activity of enzyme dipeptidyl peptidase IV according BIOPEP database. These results showed that β-lactoglobulin peptides obtained by chymotrypsin hydrolysis could have biological activity that can be used in different types of industries as pharmaceutical and food. Limitations on study/implications: The in vitro evaluation of the biological activity of the characterized peptides is necessary.

Kinetic Modeling of the Formation of Peptide Nanoparticles by Tryptic Hydrolysis of Β-Casein

Peptide nanoparticles obtained by the enzymatic hydrolysis of proteins are new biocompatible nontoxic systems for the transport of biologically active compounds. The formation of peptide nanoparticles from -casein during its controlled hydrolysis by trypsin was modeled by the methods of chemical kinetics. The product of the time of nanoparticle formation (tmax) by the enzyme concentration (E0) was analyzed in different kinetic models. The dependence of tmax∙E0 on the enzyme concentration was used to estimate the contribution of the enzymatic and non-enzymatic stages to the formation of nanoparticles.

Role of endopeptidases in peptidoglycan synthesis mediated by alternative cross-linking enzymes in Escherichia coli

ABSTRACTBacteria resist to the turgor pressure of the cytoplasm through a net-like macromolecule, the peptidoglycan, made of glycan strands connected via peptides cross-linked by penicillin-binding proteins (PBPs). We recently reported the emergence of β-lactam resistance resulting from a bypass of PBPs by the YcbB L,D-transpeptidase (LdtD), which form chemically distinct 3→3 cross-links compared to 4→3 formed by PBPs. Here we show that peptidoglycan expansion requires controlled hydrolysis of cross-links and identify amongst eight endopeptidase paralogues the minimum enzyme complements essential for bacterial growth with 4→3 (MepM) and 3→3 (MepM and MepK) cross-links. Purified Mep endopeptidases unexpectedly displayed a 4→3 and 3→3 dual specificity implying recognition of a common motif in the two cross-link types. Uncoupling of the polymerization of glycan chains from the 4→3 cross-linking reaction was found to facilitate the bypass of PBPs by YcbB. These results illustrate the plasticity of the peptidoglycan polymerization machinery in response to the selective pressure of β-lactams.

A systematic study of halide-template effects in the assembly of lanthanide hydroxide cluster complexes with histidine

Controlled hydrolysis of lanthanide ions in the presence of histidine and halide templates of different sizes produced dodeca- and pentadecanuclear lanthanide hydroxide clusters.

Red emissive sulfone-rhodols as mitochondrial imaging agents

The controlled hydrolysis of sulfone-rhodamines affords a series of core-modified red-emitting rhodols, the fluorescence of which is sensitive to solvent polarity with pronounced bathochromic shifts recorded in both DMSO and...

Characterization and evaluation of the photocatalytic activity of oxides based on TiO2 synthesized by hydrolysis controlled by the use of water/acetone mixtures

New photocatalysts based on TiO2 were synthesized and characterized. The synthesis involved the controlled hydrolysis of titanium tetraisopropoxide using water containing different proportions of acetone. X-ray diffraction analyses combined with Raman spectroscopy revealed crystalline oxides characterized by the coexistence of the anatase and brookite phases. The Rietveld refinement of diffractograms showed that the presence of acetone in the synthesis process influenced the composition of these crystalline phases, with the proportion of brookite growing from 13% to 22% with the addition of this solvent in the synthesis process. The BET isotherms revealed that these materials are mesoporous with surface area approximately 12% higher than that of the oxide prepared from hydrolysis using pure water. The photocatalytic potential of these oxides was evaluated by means degradation tests using the dyes Ponceau 4R and Reactive Red 120 as oxidizable substrates. The values achieved using the most efficient photocatalyst among the synthesized oxides were, respectively, 83% and 79% for mineralization, and 100% for discoloration of these dyes. This same oxide loaded with 0.5% of platinum and suspended in a 5:1 v/v water/methanol mixture, produced 56 mmol of gaseous hydrogen in 5 h of reaction, a specific hydrogen production rate of 138.5 mmol h−1g−1, a value 60% higher than that achieved using TiO2 P25 under similar conditions.