Contribution of Model Organisms to Investigating the Far-Reaching Consequences of PRPP Metabolism on Human Health and Well-Being.

Phosphoribosyl pyrophosphate synthetase (PRS EC 2.7.6.1) is a rate-limiting enzyme that irreversibly catalyzes the formation of phosphoribosyl pyrophosphate (PRPP) from ribose-5-phosphate and adenosine triphosphate (ATP). This key metabolite is required for the synthesis of purine and pyrimidine nucleotides, the two aromatic amino acids histidine and tryptophan, the cofactors nicotinamide adenine dinucleotide (NAD+) and nicotinamide adenine dinucleotide phosphate (NADP+), all of which are essential for various life processes. Despite its ubiquity and essential nature across the plant and animal kingdoms, PRPP synthetase displays species-specific characteristics regarding the number of gene copies and architecture permitting interaction with other areas of cellular metabolism. The impact of mutated PRS genes in the model eukaryote Saccharomyces cerevisiae on cell signalling and metabolism may be relevant to the human neuropathies associated with PRPS mutations. Human PRPS1 and PRPS2 gene products are implicated in drug resistance associated with recurrent acute lymphoblastic leukaemia and progression of colorectal cancer and hepatocellular carcinoma. The investigation of PRPP metabolism in accepted model organisms, e.g., yeast and zebrafish, has the potential to reveal novel drug targets for treating at least some of the diseases, often characterized by overlapping symptoms, such as Arts syndrome and respiratory infections, and uncover the significance and relevance of human PRPS in disease diagnosis, management, and treatment.

A review on garcinia kola heckel: traditional uses, phytochemistry, pharmacological activities, and toxicology.

PURPOSE: Garcinia kola is a medicinal plant commonly known as bitter kola. It is utilised in ethnomedicine for the treatment of diarrhoea, bronchitis, bacterial infection, cough, hepatitis, gonorrhoea, laryngitis, food poison, liver and gastric diseases. OBJECTIVE: This study reviewed the phytochemistry, pharmacological activities, and ethnomedicinal potentials of G. kola. MATERIALS AND METHODS: An extensive review was performed using electronic literature collated from ScienceDirect, Springer, Wiley, and PubMed databases. RESULTS: Phytochemical analysis revealed the isolation of several chemical compounds including 9-octadecenoic acid, linoleic acid, 14-methylpentadecanoic acid, 1-butanol, hexadecanamide, I-4',II-4',I-5,II-5,I-7,II-7-hexahydroxy-I-3,II-8-biflavanone, lanost-7-en-3-one, kolaflavanone (8E)-4-geranyl-3,5-dihydroxybenzophenone, glutinol, Garcinia biflavonoid (GB-2a-II-4'-OMe), 9,19-cyclolanost-24-en-3-ol, 24-methylene, tirucallol, lupeol, ß-amyrin, obtusifoliol and Kolaviron. Diverse pharmacological in-vivo and in vitro investigations revealed that G. kola has anti-inflammatory, antimalarial, hepatoprotective, cardioprotective, anti-asthmatic, neuroprotective, antioxidant, and antidiabetic activities. CONCLUSION: The present study revealed that G. kola has preventive and therapeutic potentials against various diseases in both in vivo and in vitro studies and therefore can be utilised as a raw material in the pharmaceutical industries for the development of therapeutic products. However, there is a need for clinical trial experiments to validate and provide accurate and substantial information on the required safe dosage and efficacy for the treatment of several diseases.

A review on the clinical trials of repurposing therapeutic drugs, mechanisms and preventive measures against SARS-CoV-2.

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is a highly transmittable pathogenic viral infection that causes a disease known as COVID-19. It is a pandemic and public health challenge ravaging the world today. Unfortunately, with the daily increase of infected individuals, there is no known drug approved for the treatment of COVID-19. However, there are therapeutic drugs with the potentials to inhibit endocytic pathways, suppress ribonucleic acid (RNA) polymerase activities, and reduce the replication of SARS-CoV-2. These drugs modifications are aimed at reducing inflammation, time of recovery, and number of deaths. This review is aimed at providing updated information on the clinical manifestations, diagnosis, preventive measures and therapeutic drugs used against SARS-CoV-2. The finding of this review revealed that some of these drugs are transmembrane protease, serine 2, and angiotensin-converting enzyme 2 inhibitors with the capacity to block the entrance/replication of SARS-CoV-2 in a host cell and therefore, may be promising in preventing the spread and mortality of SARS-CoV-2. However, these drugs may cause detrimental health effects such as toxic and non-efficacy issues. Therefore great caution should be employed by health professionals when prescribing these drugs to COVID-19 patients.

Evaluation of the safety of oral intake of aqueous extract of Stigma maydis (corn silk) in rats.

BACKGROUND: Corn silk (Stigma madyis) is used in ethnomedicine for the management of diabetes, kidney stones, depression, fatigue, urinary infections and as a slimming tea. However, there is limited literature on its effect on body weight, lipid, hematological, hepatocellular, nephrological and histopathological indices which the present study evaluated. METHODS: In the acute toxicity test, aqueous extract of Stigma madyis was orally adminis- tered to rats using a gavage, in doses of up to 5 g/kg body weight. The rats were observed for any behavioral changes, signs of toxicity or mortality. In the sub-acute toxicity, rats were orally administered 500, 1000 and 2000 mg/kg Stigma madyis extract for 28 days. On the 29th day, the rats were euthanized and the following parameters measured; lipid profile, hematology, serum chemistry and histopathology of the liver and kidney. RESULTS: In the acute toxicity test, Stigma madyis did not cause any mortality and was non-toxic at the dose of up to 5 g/kg body weight. In the sub-acute study,  the extract caused an observable significant increase   (p < 0.05) in triglycerides (TAG), low density lipoprotein (LDL) and very low density lipoprotein (VLDL), while the concentration of high density lipoprotein (HDL) decreased significantly (p < 0.05) when compared to the control group. AST and ALT increased significantly (p < 0.05) in rats treated with 1000 and 2000 mg/kg of Stigma maydis compared to their control. The histopathological results revealed degenerative changes in the liver at 2000 mg/kg body weight extract. CONCLUSIONS: In long term treatment, toxic effects were observed in liver at the doses of 1000 and 2000 mg/kg. This study suggests that prolonged use of higher doses of aqueous extract of Stigma maydis ≥ 1000 mg/kg could be hepatotoxic. Therefore, only lower doses should be encouraged for therapeutic use.

Metabolic gene products have evolved to interact with the cell wall integrity pathway in Saccharomyces cerevisiae.

Two of the five unlinked genes theoretically capable of encoding 5-phosphoribosyl-1(α)-pyrophosphate (PRPP) synthetase (Prs) in Saccharomyces cerevisiae, PRS1 and PRS5, contain in-frame insertions which separate the cation- and PRPP-binding sites, diagnostic of Prs polypeptides. The impairment of cell wall integrity (CWI) mitogen-activated protein kinase (MAPK) cascade in strains lacking PRS1 and the synthetic lethality associated with loss of PRS1 and PRS5 imply that these insertions are not gratuitous. Coimmunoprecipitation revealed that Prs1 interacts with the CWI MAPK pathway, only when Slt2 has been phosphorylated by Mkk1/2. Three serine residues identified by phosphoproteome analysis (Ficarro et al 2002) are located in one of the insertions of PRS5 thereby defining Prs5 as one of the 11 triply phosphorylated proteins in yeast. Mutation of these phosphosites compromised the transcriptional readout of one endpoint of the CWI pathway, Rlm1, as well as the expression of the gene encoding the stress-activated 1,3 ß-glucan synthase, Fks2, regulated by a second endpoint of the CWI pathway, Swi4/Swi6 (SBF transcription factor). Therefore, the unexpected impairment of the CWI phenotype encountered in yeast strains either mutated or deleted for PRS1 or PRS5 can be explained by disruption of the communication between primary cell metabolism and CWI signalling.

The contribution of the nonhomologous region of Prs1 to the maintenance of cell wall integrity and cell viability.

The gene products of the five-membered PRS gene family in Saccharomyces cerevisiae have been shown to exist as three minimal functional entities, Prs1/Prs3, Prs2/Prs5, and Prs4/Prs5, each capable of supporting cell viability. The Prs1/Prs3 heterodimer can be regarded as the most important because its loss causes temperature sensitivity. It has been shown that the GFP signal generated by an integrated GFP-Prs1 construct is lost in the absence of Prs3. In addition to interacting with Prs3, Prs1 also interacts with Slt2, the MAPK of the cell wall integrity (CWI) pathway. Lack of the nonhomologous region (NHR1-1) located centrally in Prs1 abolished the temperature-induced increase in Rlm1 expression. Furthermore, in vitro point mutations generated in PRS1 corresponding to missense mutations associated with human neuropathies or in the divalent cation and/or 5-phosphoribosyl-1(α)-pyrophosphate binding sites also display increased Rlm1 expression at 30 °C and 37 °C and most give rise to caffeine sensitivity. Human PRPS1 cDNA cannot rescue the synthetic lethality of a prs1Δ prs5Δ strain because it lacks sequences corresponding to NHR1-1 of yeast Prs1. The correlation between caffeine sensitivity and increased basal expression of Rlm1 in the altered versions of PRS1 can be extended to their inability to rescue the synthetic lethality of a prs1Δ prs5Δ strain implying that impaired CWI may contribute to the observed loss of viability.