Biochemical Activity of PIF1 Helicase from Thermophilic Bacteria / 中国生物化学与分子生物学报

Petite integration frequency 1 (PIF1) helicases are ubiquitous enzymes which play vital roles in nearly all DNA metabolic processes. In recent years, the biochemical activity and three-dimensional structure of several PIF1 helicases have been reported, but there are few reports on the PIF1 helicase of bacteria living in extreme environments. In this paper, a series of biochemical and biophysical techniques were used to study the Thermodesulfovibrio yellowstonii PIF1 (Ty.PIF1) helicase in many aspects. Ty. PIF1 was obtained with a purity of over 90% and good uniformity using the prokaryotic expression and purification system. Ty.PIF1 is a monomer with a calculated molecular weight of 60 kD in solution. Ty. PIF1 has high thermal stability. The secondary structure remains stable when the temperature is below 65 ℃, and the secondary structure changes only when the temperature is above 70 ℃. The optimal unwinding temperature of Ty.PIF1 in vitro is 45 ℃, which is not the optimal temperature for the survival of thermodesulfovibrio yellowstonii. It indicates that when Ty.PIF1 exerts its enzymatic activity in vivo, it may require the participation of other cofactors. Ty.PIF1 can exert unwinding activity in a wide temperature range (20-55 ℃), and the presence of enzyme activity at 55 ℃ indicates that Ty.PIF1 has heat-resistant properties. Ty.PIF1 prefers to bind to substrates containing ssDNA, but there is certain requirement for the length of the ssDNA, which is at least 4 nt in length. Ty.PIF1 can also bind to the G

Human carboxylesterases: a comprehensive review

Mammalian carboxylesterases (CEs) are key enzymes from the serine hydrolase superfamily. In the human body, two predominant carboxylesterases (CES1 and CES2) have been identified and extensively studied over the past decade. These two enzymes play crucial roles in the metabolism of a wide variety of endogenous esters, ester-containing drugs and environmental toxicants. The key roles of CES in both human health and xenobiotic metabolism arouse great interest in the discovery of potent CES modulators to regulate endobiotic metabolism or to improve the efficacy of ester drugs. This review covers the structural and catalytic features of CES, tissue distributions, biological functions, genetic polymorphisms, substrate specificities and inhibitor properties of CES1 and CES2, as well as the significance and recent progress on the discovery of CES modulators. The information presented here will help pharmacologists explore the relevance of CES to human diseases or to assign the contribution of certain CES in xenobiotic metabolism. It will also facilitate medicinal chemistry efforts to design prodrugs activated by a given CES isoform, or to develop potent and selective modulators of CES for potential biomedical applications.