Substitution of Asp29 with Asn29 in the metallochaperone UreE of Streptococcus thermophilus DSM 20617 < sup > T < /sup > increases the urease activity and anticipates urea hydrolysis during milk fermentation

Int J Food Microbiol. 2024 Mar 16;416:110684. doi: 10.1016/j.ijfoodmicro.2024.110684. Online ahead of print.ABSTRACTUrease operon is highly conserved within the species Streptococcus thermophilus and urease-negative strains are rare in nature. S. thermophilus MIMO1, isolated from commercial yogurt, was previously characterized as urease-positive Ni-dependent strain. Beside a mutation in ureQ, coding for a nickel ABC transporter permease, the strain MIMO1 showed a mutation in ureE gene which code for a metallochaperone involved in Ni delivery to the urease catalytic site. The single base mutation in ureE determined a substitution of Asp29 with Asn29 in the metallochaperone in a conserved protein region not involved in the catalytic activity. With the aim to investigate the role Asp29vs Asn29 substitution in UreE on the urease activity of S. thermophilus, ureE gene of the reference strain DSM 20617T (ureEDSM20617) was replaced by ureE gene of strain MIMO1 (ureEMIMO1) to obtain the recombinant ES3. In-gel detection of urease activity revealed that the substitution of Asp29 with Asn29 in UreE resulted in a higher stability of the enzyme complexes. Moreover, the recombinant ES3 showed higher level of urease activity compared to the wildtype without any detectable increase in the expression level of ureC gene, thus highlighting the role of UreE not only in Ni assembly but also on the level of urease activity. During the growth in milk, the recombinant ES3 showed an anticipated urea...
Source: International Journal of Food Microbiology - Category: Food Science Authors: Source Type: research