Sepsis refers to a life-threatening organ dysfunction caused by a dysregulated host response to infection,with persistently high morbidity and mortality,posing a significant healthcare burden.As integral components of innate and adaptive immunity,macrophages exhibit high plasticity and can differentiate into distinct phenotypes(M1 pro-inflammatory and M2 anti-inflammatory)in response to various environmental stimuli,playing crucial roles in both the hyperinflammatory phase and late immunosuppressive phase of sepsis.The metabolic profile of M2 macrophages has gradually become a research focus,and it is regulated by a variety of enzymes and signaling pathways,including adenosine 5'-monophosphate-activated protein kinase,peroxisome proliferator-activated receptor and protein kinase RNA-like ER kinase pathways.These pivotal signaling pathways and enzymes can promote the polarization of M2 macrophages and enhance their anti-inflammatory functions by modulating the metabolism of glucose,lipid,and amino acid,thereby conferring protective effects against sepsis and providing new ideas for the targeted treatment.

Creatinine levels in biological fluids are important indicators for the clinical evaluation of renal function. Creatinase (CRE, EC3.5.3.3) is one of the key enzymes in the enzymatic measurement of creatinine concentration, and it is also the rate-limiting enzyme in the whole enzymatic cascade system. The poor catalytic activity of CRE severely limits its clinical and industrial applications. To address this issue, a semi-rational design is applied to increase the activity of a creatinase from Alcaligenes sp. KS-85 (Al-CRE). By high-throughput screen of saturation mutagenesis libraries on the selected hotspot mutations, multiple variant enzymes with increased activity are obtained. The five-point best variant enzyme (I304L/F395V/K351V/Y63S/Q88A) were further obtained by recombine the improved mutations sites that to showed a 2.18-fold increased specific activity. Additionally, structure analysis is conducted to understand the mechanism of the activity change. This study paves the way for a better practical application of creatinase and may help further understand its catalytic mechanism.
Creatinine ; Mutagenesis, Site-Directed ; Ureohydrolases/genetics* ; Catalysis