Validated HPLC-Fl Method for the Analysis of S-Adenosylmethionine and S-Adenosylhomocysteine Biomarkers in Human Blood

Compatibility and stability of ademetionine 1,4-butanedisulfonate injection mixed with fructose and glucose diluents and pilot study of long-term storage impurities by LC-MS/MS

Fructose injection is occasionally used to dilute ademetionine 1,4-butanedisulfonate injection for patients who cannot receive glucose or sodium chloride injections in clinical settings. Since our PIVAS staff reported that discoloration occurred after ademetionine 1,4-butanedisulfonate dissolved with fructose injection, this study aims to investigate the stability of ademetionine 1,4-butanedisulfonate in fructose and glucose solutions. Ademetionine 1,4-butanedisulfonate was purchased and diluted with fructose or glucose injection for compatibility testing. The solutions were maintained under various conditions for different periods of time, after which the concentration of ademetionine 1,4-butanedisulfonate and other impurities was analyzed. The chemical structures of unknown impurities were further investigated by liquid chromatography-tandem mass spectrometry. The analytical method was validated and was deemed to be suitable for the analyses in this study. Compatibility tests indicated that ademetionine 1,4-butanedisulfonate is sensitive to temperature, illumination, and pH. When diluted with fructose or glucose, the concentration of ademetionine 1,4-butanedisulfonate decreased over time. The contents of impurities increased accordingly. Additionally, an unknown impurity was identified, speculated to be a hydroxyl oxidation product of ademetionine based on the LC-MS/MS results. Both fructose and glucose injections can be used as diluents for ademetionine 1,4-butanedisulfonate, and the resulting mixture remains stable for up to 8 h after preparation.

The functional roles of S-adenosyl-methionine and S-adenosyl-homocysteine and their involvement in trisomy 21

The one-carbon metabolism pathway is involved in critical human cellular functions such as cell proliferation, mitochondrial respiration, and epigenetic regulation. In the homocysteine-methionine cycle S-adenosyl-methionine (SAM) and S-adenosyl-homocysteine (SAH) are synthetized, and their levels are finely regulated to ensure proper functioning of key enzymes which control cellular growth and differentiation. Here we review the main biological mechanisms involving SAM and SAH and the known related human diseases. It was recently demonstrated that SAM and SAH levels are altered in plasma of subjects with trisomy 21 (T21) but how this metabolic dysregulation influences the clinical manifestation of T21 phenotype has not been previously described. This review aims at providing an overview of the biological mechanisms which are altered in response to changes in the levels of SAM and SAH observed in DS.

Chemical biology and medicinal chemistry of RNA methyltransferases

RNA methyltransferases (MTases) are ubiquitous enzymes whose hitherto low profile in medicinal chemistry, contrasts with the surging interest in RNA methylation, the arguably most important aspect of the new field of epitranscriptomics. As MTases become validated as drug targets in all major fields of biomedicine, the development of small molecule compounds as tools and inhibitors is picking up considerable momentum, in academia as well as in biotech. Here we discuss the development of small molecules for two related aspects of chemical biology. Firstly, derivates of the ubiquitous cofactor S-adenosyl-l-methionine (SAM) are being developed as bioconjugation tools for targeted transfer of functional groups and labels to increasingly visible targets. Secondly, SAM-derived compounds are being investigated for their ability to act as inhibitors of RNA MTases. Drug development is moving from derivatives of cosubstrates towards higher generation compounds that may address allosteric sites in addition to the catalytic centre. Progress in assay development and screening techniques from medicinal chemistry have led to recent breakthroughs, e.g. in addressing human enzymes targeted for their role in cancer. Spurred by the current pandemic, new inhibitors against coronaviral MTases have emerged at a spectacular rate, including a repurposed drug which is now in clinical trial.

Measurement of homocysteine: a historical perspective

Elevated plasma level of homocysteine is being increasingly associated with many diseases. There is a significant interest in the development of methods to determine the total homocysteine in biologically relevant tissues. Over the years, researchers use various methods to determine the exact concentrations of homocysteine in these tissues. However, the precise method used in many studies earlier was questionable. We have reviewed various methodologies for the measurement of homocysteine. We list the commonly used methodologies currently in use to determine homocysteine levels. Through extensive literature search, we have come up with the most popular as well as the newest measurement modalities and listed them with a brief discussion of each of the methodology. In conclusion, we have presented the historical perspective of homocysteine measurement in biological fluids in this manuscript. Thus, the precise understanding of its concentration in biological fluids coupled with its importance in health and disease should justify a newer but reliable technique in the area of ongoing research in homocysteine.

Determination of S-adenosylmethionine and S-adenosylhomocysteine in blood plasma by UPLC with fluorescence detection

A validated approach to determine various methionine cycle metabolites (S-adenosylmethionine, S-adenosylhomocysteine, and methylthioadenosine) in human blood plasma is offered. The approach is based on solid-phase extraction (with grafted phenylboronic acid) and derivatization with chloroacetaldehyde followed by ultra-performance liquid chromatography with fluorescence detection. We used a 100 × 2.1 mm × 1.8 μm C18 column for the selective separation of analytes. Chromatographic separation was achieved with gradient elution of acetonitrile (flow rate 0.2 mL/min) from 2 to 20%. The eluent was initially composed of 10 mM KH₂PO₄ with 10 mM acetic acid and 25 μM heptafluorobutyric acid. The total analysis time was 11 min. Validation of the method included detection of the limit of detection (2 nM), limit of quantification (5 nM), accuracy (97.2-101%), and intra- and interday precision (2.2-9.0%). Analysis of plasma samples from healthy volunteers revealed that the average levels of S-adenosylmethionine, S-adenosylhomocysteine, and methylthioadenosine were 93.6, 20.9 and 14.8 nM, respectively.

Quantitative analysis of drugs in biological matrices by HPLC hyphenated to fluorescence detection

An overview of the state-of-the art in HPLC coupled with fluorescence detection is presented. Over the last 20 years, the increasing number of methodological papers on this topic (4082 between 1994 and 2004 and 7725 between 2004 and 2014) is testament to its utility in bioanalytical applications. Compared with conventional UV absorbance detection used in HPLC, fluorescence detection can greatly enhance the sensitivity leading to limits of detection similar to those obtained with mass spectrometry, offering researchers a sensitive, robust and relatively inexpensive instrumental method. This work will focus on the analysis of pharmaceutical compounds in different biological matrices, either naturally fluorescent or derivatized with a fluorescent agent, and some of them chiral. Therapeutic applications, sample preparation and derivatization, sensitivity for each example are described.

A thermostable S-adenosylhomocysteine hydrolase from Thermotoga maritima: properties and its application on S-adenosylhomocysteine production with enzymatic cofactor regeneration

S-adenosylhomocysteine (SAH) is an effective sedative, a good sleep modulator, and a new anticonvulsant. SAH can be synthesized from adenosine and homocysteine by using microbial S-adenosylhomocysteine hydrolase (SAHase). The extremely thermostable SAHase and lactate dehydrogenase (LDH) from Thermotoga maritima were successfully overexpressed in Escherichia coli, and purified by heat treatments. The SAHase exhibited the highest activity at 85 °C and pH 8.0 with a specific activity of 6.2 U/mg when NAD concentration was 1mM. However, optimal SAHase reaction conditions shifted to 100 °C and pH 11.2, and its specific activity increased to 36.8 U/mg after NAD concentration was raised to 8mM. Biosynthesis of SAH at 85 °C largely increased the adenosine solubility which was a limiting factor for improving the titer of product. At 85 °C and pH 8.0, 24 μmol of SAH was obtained when 0.5mg of SAHase was applied to a 10 ml reaction mixture. The SAH production was further increased to 153 μmol by adding LDH and pyruvate into the reaction mixture for NAD regeneration. Therefore, extremely thermostable enzymes SAHase and LDH from T. maritima form an efficient NAD consumption and regeneration system for SAH biosynthesis. This method has great potential for industrial-scale enzymatic production of SAH.