Structural and Mutational Analyses of Trehalose Synthase from Deinococcus radiodurans Reveal the Interconversion of Maltose-Trehalose Mechanism.

Trehalose synthase (TreS) catalyzes the reversible interconversion of maltose to trehalose, playing a vital role in trehalose production. Understanding the catalytic mechanism of TreS is crucial for optimizing the enzyme activity and enhancing its suitability for industrial applications. Here, we report the crystal structures of both the wild type and the E324D mutant of Deinococcus radiodurans trehalose synthase in complex with the trehalose analogue, validoxylamine A. By employing structure-guided mutagenesis, we identified N253, E320, and E324 as crucial residues within the +1 subsite for isomerase activity. Based on these complex structures, we propose the catalytic mechanism underlying the reversible interconversion of maltose to trehalose. These findings significantly advance our comprehension of the reaction mechanism of TreS.

Molecular characterization of extended-spectrum beta-lactamase-producing Escherichia coli isolates from chickens in Henan Province, China.

Extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli has spread rapidly worldwide and poses a serious threat to human and animal health. This study collected 51 non-replicate E. coli isolates from 14 different chicken farms in Henan Province in China from December 2007 to August 2008. The prevalence of ESBL-producing E. coli, molecular characterization of the ESBL-related bla genes, including bla(TEM), bla(SHV) and bla(CTX-M), and the susceptibilities of these bacteria to various antimicrobial agents were determined. Thirty-one of the 51 isolates were positive for an ESBL phenotype and 29 of these isolates carried one or more bla genes. Twenty-two isolates harboured bla(TEM) genes and 15 isolates carried bla(CTX-M) genes (one CTX-M-14, three CTX-M-24 and 11 CTX-M-65). One isolate carried bla(TEM)(-57); the remaining bla(TEM) isolates carried bla(TEM-1) with one silent nucleotide base variation (T18C). We believe that this is the first study to report TEM-57 in E. coli isolates. All isolates harbouring bla(CTX-M-24) and bla(CTX-M-14) and five of the bla(CTX-M-65) isolates also harboured the bla(TEM-1) gene. To our knowledge, this study is the first to describe detection of CTX-M-65-producing E. coli isolated from chickens. None of the isolates contained the bla(SHV) gene. Conjugation experiments demonstrated that bla(CTX-M) and bla(TEM) genes could be transferred to E. coli DH5 alpha. The results indicate that ESBL frequency has reached an alarming level in chicken isolates in China, with TEM-1 and CTX-M-65 enzymes being the two predominant beta-lactamases detected.

[Influence on the concentration of plasma endotoxin by inhibition of complement activation in traumatic hemorrhagic shock rats].

OBJECTIVE: To investigate the influence on the concentration of plasma endotoxin by inhibition of complement activation in traumatic hemorrhagic shock rats. METHODS: Eighty male SD rats were randomly divided into two groups: control and cobra venom factor (CVF) treatment groups. The hemorrhagic shock induced by trauma was replicated in both groups. The animals were killed preshock and at 1, 6, and 24 hours postresuscitation. Twenty-four hours before hemorrhage, rats were given a mainline dose of either 50 microg/kg CVF or an equal volume of saline solution. The plasma and serum samples were collected at each time point to determine the concentration of endotoxin, the activity of CH50 and diamine oxidase (DAO), and the level of tumor necrosis factor (TNF-alpha) at various time points in two groups. RESULTS: Compared with preshock in control group, serum CH50 levels were decreased promptly at 1 hour postresuscitation. Markedly elevation of the levels of endotoxin and TNF-alpha in blood were found at early time after resuscitation, and they were come rapidly back to the basic level at 6 and 24 hours phase. The activity of DAO in blood was increased significantly at 1 and 6 hours after resuscitation and declined promptly at 24 hours. Compared with the control group, significantly decline of the levels of endotoxin, TNF-alpha and DAO at the various time points after resuscitation were also found in the CVF group. The levels of CH50 in CVF group were always less than 5% during the experiment. CONCLUSION: In traumatic hemorrhagic shock rats CVF pretreatment could decline plasma endotoxin levels by preventing the injury of intestine and gut barrier function, decrease endotoxin translocation and reduce plasma endotoxin levels.