The characteristics of protein-glutaminase from an isolated Chryseobacterium cucumeris strain and its deamidation application

Abstract

Protein-glutaminase (PG), a deamidation enzyme commercially derived from Chryseobacterium proteolyticum, is used to improve the solubility and other functional properties of food proteins. In this study, a new PG-producing strain, Chryseobacterium cucumeris ZYF120413-7, was isolated from soil, and it had a high PG yield and a short culture time. It gave the maximum PG activity with 0.557 U/ml on Cbz-Gln-Gly after 12 h of culture, indicating that it was more suitable for PG production. The enzyme activity recovery and purification fold were 32.95% and 161.95-fold, respectively, with a specific activity of 27.37 U/mg. The PG was a pre-pro-protein with a 16 amino acids putative signal peptide, a pro-PG of 118 amino acids, and a mature PG of 185 amino acids. The amino acid sequence identity of PG from strain ZYF120413-7 was 74 and 45%, respectively, to that of PG from C. proteolyticum 9670T and BH-PG. The optimum reaction pH and temperature of PG was 6 and 60°C, respectively. Enzyme activity was inhibited by Cu2+. The optimum PG substrate was Cbz-Gln-Gly, and the Km and Vmax values were 1.68 mM and 1.41 μM mg protein−1 min−1, respectively. Degree of deamidation (DD) of soy protein isolate (SPI) treated by purified PG was 40.75% within the first 2 h and 52.35% after 18 h. These results demonstrated that the PG from C. cucumeris ZYF120413-7 was a promising protein-deamidating enzyme for improving the functionality of food proteins.

Recombinant Protein Glutaminase from Probiotic Escherichia coli Nissle 1917 for Enhancing the Functional Properties of Caseins

“…PG enzyme activity assay was referenced to Qu et al with slight modi cations (Qu, et al, 2022). 10 µl solution containing PG was reacted with 100 µl of Cbz-Gln-Gly (10.11 g/L) of the experimental group or inactivated with 100 µl of 1 N TCA of the control group at 37°C for 30 min.…”

“…Currently, The maximum PG enzyme activity of 0.175 U/mL was achieved in E. coli (Lu, et al, 2020). The PG enzyme activity of 7.07 U/mL and 26 U/mg were achieved in Bacillus subtilis (Ouyang, et al, 2021;Yin, et al, 2021) and Corynebacterium glutamicum (Kikuchi, et al, 2008;Qu, et al, 2022;Wang, et al, 2023), respectively. Unfortunately, the expression effect of E. coli, which is the preferred host for superior heterologous gene expression, seems to be not optimistic for PG production.…”