Effect of glutaraldehyde on the activity of some DNA restriction endonucleases

Human aldehyde dehydrogenase 3A1 (ALDH3A1) exhibits chaperone-like function

Aldehyde dehydrogenase 3A1 (ALDH3A1) is a metabolic enzyme that catalyzes the oxidation of various aldehydes. Certain types of epithelial tissues in mammals, especially those continually exposed to environmental stress (e.g., corneal epithelium), express ALDH3A1 at high levels and its abundance in such tissues is perceived to help to maintain cellular homeostasis under conditions of oxidative stress. Metabolic as well as non-metabolic roles for ALDH3A1 have been associated with its mediated resistance to cellular oxidative stress. In this study, we provide evidence that ALDH3A1 exhibits molecular chaperone-like activity further supporting its multifunctional role. Specifically, we expressed and purified the human ALDH3A1 in E. coli and used the recombinant protein to investigate its in vitro ability to protect SmaI and citrate synthase (from precipitation and/or deactivation) under thermal stress conditions. Our results indicate that recombinant ALDH3A1 exhibits significant chaperone function in vitro. Furthermore, over-expression of the fused histidine-tagged ALDH3A1 confers host E. coli cells with enhanced resistance to thermal shock, while ALDH3A1 over-expression in the human corneal cell line HCE-2 was sufficient for protecting them from the cytotoxic effects of both hydrogen peroxide and tert-butyl hydroperoxide. These results further support the chaperone-like function of human ALDH3A1. Taken together, ALDH3A1, in addition to its primary metabolic role in fundamental cellular detoxification processes, appears to play an essential role in protecting cellular proteins against aggregation under stress conditions.

Cyclophilin-40 has a cellular role in the aryl hydrocarbon receptor signaling

Cyclophilin-40 (CyP40) promotes the formation of the gel shift complex that contains the aryl hydrocarbon receptor (AhR), AhR nuclear translocator (Arnt) and dioxin response element (DRE) using baculovirus expressed proteins. Here we reported that CyP40 plays a role in the AhR signaling. When the CyP40 content in MCF-7 cells is reduced, up-regulation of cyp1a1 and cyp1b1 by 3-methylchloranthrene (3MC) is also reduced, suggesting that CyP40 is essential for maximal AhR function. The CyP40 region containing amino acids 186-215, but not the peptidyl-prolyl cis-trans isomerase and tetratricopeptide repeat domains, is essential for forming the AhR/Arnt/DRE complex. CyP40 is found in the cell nucleus after 3MC treatment and appears to promote the DRE binding form of the AhR/Arnt heterodimer.

Immobilized nucleases

Nucleases are important analytical enzymes and are used widely for the determination of nucleic acid structure. Their application depends on the specificity and mode of action of the particular enzyme. Nucleases have also found application in the production of flavor enhancers like 5' IMP and 5' GMP, removal of nucleic acids in single cell protein preparations, and as therapeutic agents. Immobilization of nucleases and the use of immobilized nucleases for various biotechnological applications have been reviewed.

Immobilization of the restriction endonucleases PvuII and HindIII

The effects of several chemical reagents on the activity of the restriction endonucleases PvuII and HindIII were investigated. Carbodiimide, which reacts preferentially with carboxyl groups, was found to inactivate these enzymes. This specific effect could be prevented by Mg2+ cation. pBR322 DNA, which contains PvuII and PvuII* sites and HindIII and HindIII* sites, did not protect the enzymes from the carbodiimide. On the other hand, glutaraldehyde, which reacts primarily with lysine residues, inactivates PvuII and HindIII enzymes. This specific effect could not be prevented by pBR322 DNA. Preincubation with high concentrations of N-ethylmaleimide, which reacts with sulfhydryl groups, caused slight inhibition of PvuII activity, but had no effect on the activity of HindIII enzyme. The effects of glutaraldehyde, carbodiimide, and N-ethylmaleimide on other restriction endonucleases were also investigated. Restriction endonucleases PvuII and HindIII were immobilized by covalent coupling to various insoluble carriers. Both immobilized enzymes retained partial enzyme activities, when immobilized through phenolic groups and were stable for at least two months.