The Enzyme Gene Expression of Protein Utilization and Metabolism by Lactobacillus helveticus CICC 22171

Abstract

The purpose of this study was to explore the hydrolytic ability of Lactobacillus helveticus CICC 22171 with regard to protein and the expression of enzyme genes during protein utilization. The results revealed that the strain hydrolyzed casein from the C-terminal, reached the maximum level in 6 h, and the number of amino acids in the hydrolyzed peptide was 7–33. The molecular weight was 652.4–3432.74 kDa. Hydrophobic peptides produced by hydrolysis were the source of β-casein bitterness. Leucine and glutamine were the preferred cleavage points after 1 h; tyrosine and tryptophan subsequently increased. The first step of hydrolysis was controlled by PrtP and PrtM genes and coordinated with the action of PrtH1 and PrtH2. The transport system consisted of DtpT, OppB, OppD and OppF. The hydrolytic third step endopeptidase system consisted of the aminopeptidases (PepN, PepC, PepM and PepA), the endopeptidases (PepE, PepF and PepO); the dipeptidases (PepV and PepD), the tripeptidase PepT; the proline peptidases (PepX, PepP, PepQ, PepR and PepI). The expression of CEP genes was significantly different, and the expression level of genes related to the transport system significantly increased from 0 to 1 h. The specificity of the substrate and action site of endopeptidase was abundant.

Comparing Nutritional Values and Bioactivity of Kefir from Different Types of Animal Milk

“…In general, many LABs contain a cell-envelope proteinase (CEP) that hydrolyzes the proteins into oligopeptides, which are further degraded into shorter peptides and amino acids by intracellular peptidases. They are taken up by the kefir microorganisms or released in the surrounding media [ 61 ]. Dallas et al [ 62 ] reported that protein fragments in milk were released in part by kefir microorganisms and in part by native milk proteases.…”

Enrichment and characterization of human-associated mucin-degrading microbial consortia by sequential passage

“…In the experiments here, common vitamin auxotrophies were alleviated through addition of the ATCC vitamin supplement. However, in hand with amino acid auxotrophies, the abilities of an organism to scavenge amino acids into its cells vary; further, some organisms produce exopeptidases capable of breaking down complex proteins into smaller fragments, as dipeptides or free amino acids, which are then transported into the cell (Zhang et al 2022 ). Although the mucin backbone does provide a potential source of amino acids, not all bacteria produce peptidases able to cleave the mucin backbone.…”

“…Auxotrophy for amino acids in vitro can be alleviated through addition of free amino acids, peptides, or protein supplements. However, the ability of an organism to scavenge amino acids varies; only some organisms produce exopeptidases capable of breaking down complex proteins into smaller fragments, such as dipeptides or free amino acids, which are then transported into the cell (Zhang et al 2022 ). Therefore, variability in host diets leads to a difference in dietary fibers and amino acid sources consumed, ultimately conferring advantages to specific sets of microorganisms capable of breaking the discrete bond types and helping to shape the uniqueness of each microbiome.…”

Interindividual Diversity of Human Gut Mucin-Degrading Microbial Consortia

“…In the experiments here, common vitamin auxotrophies were alleviated through addition of the ATCC vitamin supplement. However, in hand with amino acid auxotrophies, the abilities of an organism to scavenge amino acids into its cells vary; further, some organisms produce exopeptidases capable of breaking down complex proteins into smaller fragments, as dipeptides or free amino acids, which are then transported into the cell (Zhang et al 2022). Although the mucin backbone does provide a potential source of amino acids, not all bacteria produce peptidases able to cleave the mucin backbone.…”