Complete Genome Sequence and Characterization of a Protein-Glutaminase Producing Strain, Chryseobacterium proteolyticum QSH1265

Abstract

Recently, an enzyme named protein-glutaminase (PG) has been identified as a new type of enzyme with significant potential for deamidation of food proteins. The enzyme is shown to be expressed as a pre-pro-protein with a putative signal peptide of 21 amino acids, a pro-sequence of 114 amino acids, and a mature PG of 185 amino acids. The microbial enzyme PG specifically catalyzes deamidation of proteins without protein hydrolysis pretreatment and only reacts with glutamine residues in the side-chains of proteins or long peptides. All these attributes suggest that it has a great potential for food industrial applications. However, until recently, there have been relatively few studies of the PG-producing strains. A strain named Chryseobacterium proteolyticum QSH1265 which can produce PG was isolated from a soil sample collected in Songjiang, Shanghai, China. Its enzyme activity was about 0.34 ± 0.01 U/mL when using carboxybenzoxy-Gln-Gly as a substrate. The strain can produce acid from D-glucose, maltose, L-arabinose sucrose, glycerol, and mannitol but not fructose, and it is also positive for indole production and urease. Here we describe the complete genome sequence of this strain via PacBio RSII sequencing. The C. proteolyticum QSH1265 genome consists of a circular chromosome with total length of 4,849,803 bp without any plasmids. All of 4563 genes were predicted including 4459 genes for protein-coding and 104 RNA-relative genes with an average G+C content of 36.16%. The KEGG and COG annotation provide information for the specific function of proteins encoded in the genome, such as proteases, chromoproteins, stress proteins, antiporters, etc. A highly conserved hypothetical protein shares a promoter with the gene encoding the protein-glutaminase enzyme. The genome sequence and preliminary annotation provide valuable genetic information for further study of C. proteolyticum.

Protein-Glutaminase Engineering Based on Isothermal Compressibility Perturbation for Enhanced Modification of Soy Protein Isolate

“…10 Currently, several wild strains with relatively stable activity have been screened from the soil by enrichment culture and various mutagenesis methods, such as protoplast fusion, ultraviolet (UV) mutagenesis, and nitro-Nnitrosoguanidine (NTG) mutagenesis. 17 The efficiency of enzyme production was improved, and the activity was increased from 0.34 to 2.80 units/mL. 17 In addition, the heterologous expression of PG is also an effective pathway to enhance the activity.…”

“…17 The efficiency of enzyme production was improved, and the activity was increased from 0.34 to 2.80 units/mL. 17 In addition, the heterologous expression of PG is also an effective pathway to enhance the activity. At present, PG has been successfully expressed in Escherichia coli, Bacillus subtilis, and Corynebacterium glutamicum.…”

Application Prospect of Protein-Glutaminase in the Development of Plant-Based Protein Foods

“…Deamidation by proteinglutaminase can lead to the exposure of hydrophobic sites that were previously hidden and convert the amide group to a carboxyl group, which significantly reduces intra/intermolecular hydrogen bonding and enhances electrostatic repulsion between protein molecules (Figure 1). Additionally, protein-glutaminase only reacts with glutamine residues in the side chains of proteins or short peptides and does not react with free glutamine or asparagine residues [17]. Furthermore, there are some disadvantages of other enzymatic deamidations such as peptide-glutaminase (EC 3.5.1.43) and glutaminase (EC 3.5.1.2).…”

Protein deamidation to produce processable ingredients and engineered colloids for emerging food applications

“…Its enzyme activity was about 0.34 ± 0.01 U/ml when using carboxybenzoxy (CBZ)-Gln-Gly as a substrate. However, the enzyme-producing ability of wild strains, as well as the genomic diversity and an incomplete understanding of the genetic features of C. proteolyticum, have unfortunately hindered the application of PG in the food industry (Qu et al, 2018). Most recently, a novel PG was discovered from Bacteroides helcogenes by Horstmann et al (2020).…”