Sennoside A (SA), a typical prodrug, exerts its laxative effect only after its transformation into rheinanthrone catalyzed by gut microbial hydrolases and reductases. Hydrolases have been identified, but reductases remain unknown. By linking a photoreactive group to the SA scaffold, we synthesized a photoaffinity probe to covalently label SA reductases and identified SA reductases using activity-based protein profiling (ABPP). From lysates of an active strain, Bifidobacterium pseudocatenulatum (B. pseudocatenulatum), 397 proteins were enriched and subsequently identified using mass spectrometry (MS). Among these proteins, chromate reductase/nicotinamide adenine dinucleotide (NADH) phosphate (NADPH)-dependent flavin mononucleotide (FMN) reductase/oxygen-insensitive NADPH nitroreductase (nfrA) was identified as a potent SA reductase through further bioinformatic analysis and The Universal Protein Resource (UniProt) database screening. We also determined that recombinant nfrA could reduce SA. Our study contributes to further illuminating mechanisms of SA transformation to rheinanthrone and simultaneously offers an effective method to identify gut bacterial reductases.

Objective To evaluate arterial stiffness in middle-age and elderly patients on the treatment of hemodialysis and to investigate the risk factors of arterial stiffness. Method A total of 87 in middle-age and elderly patients on the treatment of hemodialysis were enrolled. The distensibility coefficient (DC) of the common carotid artery was evaluated by an ultrasonic phase-locked echo-tracking system. Serum albumin, total cholesterol (TC), high density lipoprotein (HDL), low density lipoprotein (LDL), triglyceride (TG), glucose, creatinine,calcium, phosphorus, and intact parathyroid hormone (iPTH) were determined with well established methods. Results The ages of 87 patients ranged from 45 to 81 years, and the duration of treatment with hemodialysis was varied from 3 to 204 months . The carotid DC was ( 13.39 ± 5.32 ) × 10-3/kPa in middle-age and elderly patients on hemodialysis. In stepwise multiple regression analysis, systolic blood pressure (β = -0.349, P ＜ 0.001), age (β=-0.323, P ＜ 0.001), diabetes (β =-0.195,P = 0.027), and serum calcium (β =-0.276,P =0.002) were independently correlated with carotid DC. Conclusions Systolic blood pressure, age, diabetic,serum calcium were independent determinants for arterial stiffness of carotid artery in middle-age and elderly patients on hemodialysis.