Purification of a non-specific nucleoside hydrolase from Alaska pea seeds

Development of an approach to determining enzymatic activity of ribonucleoside hydrolase c using hydrophilic interaction liquid chromatography

Ribonucleoside hydrolase C (RihC, EC 3.2.2.1-3.2.2.3, 3.2.2.7, 3.2.2.8) belongs to the family of ribonucleoside hydrolases that catalyze the cleavage of both purine and pyrimidine ribonucleosides to nitrogenous bases and ribose. Its most efficient reaction is the cleavage of uridine with the highest reaction rate. The reaction cannot be detected by a simple spectrophotometric method because of the same absorption maximum for the substrate and reaction product or requires time- and labor-consuming sample preparation for ribose. Reversed-phase HPLC is currently used to register enzymatic activity, where the time of one chromatographic run takes about 10 min. Since a large number of analyses is required to measure the kinetics of an enzymatic reaction, the total time is significant. In this work, we obtained new recombinant RihC from Limosilactobacillus reuteri by gene cloning and expression in E.coli cells. We proposed a new approach for determining the enzymatic activity of the new RihC using hydrophilic interaction liquid chromatography (HILIC). The novel column was developed for this procedure providing the determination of uracil and uridine with high efficiency and retention times of 0.9 and 1.7 min, respectively. Kinetic parameters for RihC uridine cleavage were determined. The proposed approach provided significant rapidity for measurement of the enzyme kinetics being 5 times faster as compared to reversed-phase HPLC.

Ribonucleoside Hydrolases-Structure, Functions, Physiological Role and Practical Uses

Ribonucleoside hydrolases are enzymes that catalyze the cleavage of ribonucleosides to nitrogenous bases and ribose. These enzymes are found in many organisms: bacteria, archaea, protozoa, metazoans, yeasts, fungi and plants. Despite the simple reaction catalyzed by these enzymes, their physiological role in most organisms remains unclear. In this review, we compare the structure, kinetic parameters, physiological role, and potential applications of different types of ribonucleoside hydrolases discovered and isolated from different organisms.

Structure, Oligomerization and Activity Modulation in N-Ribohydrolases

Enzymes catalyzing the hydrolysis of the N-glycosidic bond in nucleosides and other ribosides (N-ribohydrolases, NHs) with diverse substrate specificities are found in all kingdoms of life. While the overall NH fold is highly conserved, limited substitutions and insertions can account for differences in substrate selection, catalytic efficiency, and distinct structural features. The NH structural module is also employed in monomeric proteins devoid of enzymatic activity with different physiological roles. The homo-oligomeric quaternary structure of active NHs parallels the different catalytic strategies used by each isozyme, while providing a buttressing effect to maintain the active site geometry and allow the conformational changes required for catalysis. The unique features of the NH catalytic strategy and structure make these proteins attractive targets for diverse therapeutic goals in different diseases.

Identification of new trace related impurities in adenosine products using ultra-high-performance liquid chromatography/electrospray ionization quadrupole time-of-flight tandem mass spectrometry

RATIONALE

Adenosine can induce various physiopathological effects and has been adopted as a drug to treat certain forms of supraventricular tachycardia. Adenosine is predominantly produced via fermentation that may generate many other bioactive compounds with similar structures at trace levels. Thus, it is necessary to identify these trace structurally related impurities. A new method using ultra-high-performance liquid chromatography (UHPLC) coupled with quadrupole time-of-flight tandem mass spectrometry (QTOF-MS/MS) is proposed to separate complex components at trace amounts; to obtain accurate mass measurements providing the elemental composition of unknown compounds; and MS/MS spectra for elucidation of structures.

METHODS

A UHPLC/QTOF-MS method was developed to separate and detect trace related impurities with structures similar to adenosine in formation samples. MS and MS/MS spectra of the impurities detected in real samples were acquired and used to propose their structures. Available reference standards were used to confirm the identification of some of the impurities detected.

RESULTS

Nine trace impurities of adenosine were separated and characterized. Of these nine, five were confirmed as 5'-adenylic acid, hypoxanthine, inosine, adenine, and 2'-deoxyadenosine by comparison with their available reference standards. The remaining four were proposed to be ADP-ribose, two S-epimers of 5'-deoxy-5'-methylsulfinyl adenosine, and 3'-α-glucosyl adenosine based on their MS and MS/MS spectra, and available literature. Additionally, the MS/MS fingerprints of the monosaccharide glycosyl groups were discovered and discussed.

CONCLUSIONS

A UHPLC/QTOF-MS method was established and used for the separation and characterization of nine trace related impurities of adenosine. Their structures were identified based on the MS and MS/MS spectra and retention times. In addition, the specific MS/MS fingerprints of the monosaccharide glycosyl moieties of the adenosine impurity analogs were summarized.