An overview of 3-hydroxy-3-methylglutaryl CoA reductase (HMGR) in plants

Isoprenoids biosynthesis in plants involves two separate pathways, mevalonate (MVA) pathway and 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway. A large group of isoprenoids are found to play crucial roles in common plant biochemical functions and have been produced on a large scale for commercial applications. 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) is the key enzyme that catalyses the first committing step in the MVA pathway. In mammals and yeast, HMGR is a well-studied enzyme as many studies have been done on this enzyme due to its important function in the biosynthesis of cholesterol. In plants, many researches on HMGR have been done on different plant species, for example, Arabidopsis thaliana, tobacco, gingko, Zea mays, potato, rose, rubber tree, muskmelon, ginseng and others, in the past decades since it was discovered. Previous researches that worked on plant HMGR focused on the cloning and characterisation of its physiological functions. Little is known about the aspect of regulation and structural characteristics of plants’ HMGR. This review is aimed at providing an overview of the characteristics and structure of HMGR, the transcriptional and post-translational events related to HMGR that have been reported in plants, and proposes areas on the regulation event of HMGR in plants that can be explored to further enhance understanding towards HMGR regulatory interactions

Isolation and characterization of a terpene synthase gene from bangun-bangun [Plectranthus amboinicus (Lour.) spreng.]

Plant natural products play important roles in the pharmaceutical field. Based on World Health Organization, 80% of the world population uses herbal plants as their medications to treat diseases because herbal plants are commonly accessible, effective and considered safer to be consumed by humans. Plectranthus amboinicus or bangun-bangun in Malaysia is a herbal plant and its bioactive compounds like terpenoids contributed to the properties and potential applications in the pharmaceutical field. Plant-derived terpenoids were proven by research and clinical studies to have great potentials for use as medicine and drugs. However, commercialization of plant-derived terpenoids has been challenging as they are present at low amount. This study was aimed to isolate, clone and functionally characterize the transcript of a terpene synthase gene from P. amboinicus. A novel full length transcript sesquiterpene synthase (designated as PamTPS2) was isolated, cloned and identified with an open reading frame of 1653 bp that encoded a 551 amino acids protein. The molecular weight of the deduced protein was approximately 64 kDa with an isoelectric point (pI) value of 5.68. Conserved motifs that are typically present in terpene synthases were also found in deduced PamTPS2 protein. The conserved motifs found were aspartate-rich DDXXD motif that is critical for positioning substrates, a NSE/DTE motif that can fix pyrophosphate substrate, and a RXR motif involving in the complexation of the diphosphate group after substrate ionization. Thus, it was suggested that PamTPS2 belongs to class I terpene synthase and of the TPS-b group. Besides, the 3-D protein structure of PamTPS2 was constructed using SWISS-MODEL and MODELLER 9.21 and validated via in silico analysis. It was revealed that the 3D structure ofPamTPS2 was made up of 34 α-helices, 2 β-sheets and 34 turns. Through molecular docking, it was further revealed that PamTPS2 could be a multi-substrate enzyme as it has affinity towards three potential substrates in the following order (highest to lowest), which are, farnesyl pyrophosphate, geranyl pyrophosphate and geranylgeranyl pyrophosphate. Real-time quantitative polymerase chain reaction (RT-qPCR) was performed on leaf and stems at three different timepoints 8AM, 2PM and 8PM. PamTPS2 transcript was shown to be expressed 5 folds higher in the leaf than the stems at 8AM. However, at 2PM, it was expressed around 140 folds higher in stem than leaves. The PamTPS2 cDNA was cloned into pMAL-c5x vector and expressed in Escherichia coli BL21 strain. Functional enzymatic assays were performed to analyze the potential products produced from the catalytic activity of PamTPS2. Based on in vivo enzymatic test on E. coli habouring pMAL-c5x:PamTPS2, caryophyllene and β-sesquiphellandrene were produced as final products. However, in vitro enzymatic tested on purified PamTPS2 did not show any targeted terpene products. The successful isolation of a novel functional sesquiterpene synthase from P. amboinicus would be beneficial to be applied in the pharmaceutical field

Mismatched filter for transmit waveform with frequency notches

In order to reduce radar interference on communication systems within shared bands, the radar transmit waveform forms frequency notches in the shared bands. However, because of the notches, the auto-correlation of the transmit waveform with frequency notches leads to high-range sidelobes. In order to achieve low-range sidelobes, the authors propose a mismatched filter. The mismatched filter for the transmit waveform with frequency notches has the same range sidelobes as the auto-correlation of the transmit waveform without frequency notches at the expense of a signal-to-noise ratio (SNR) loss. Simulation and analysis results demonstrate that the proposed mismatched filter always has low sidelobes at the cost of a SNR loss. In addition, simulation results show that the SNR loss is acceptable even for the deep notches (i.e. 20 dB), when the ratio of the waveform energy in the shared bands to the total waveform energy is moderate (i.e. <;8%). However, the SNR loss increases rapidly with the depth of notches, when the ratio is large.Published versio

The Sarawak Myelofibrosis (SaMy) experience: Demographics and outcome of myelofibrosis patients in Sarawak, Malaysia

Introduction: Myelofibrosis is a rare disease. There is currently no published data reporting the demographics and outcome of myelofibrosis patients in Malaysia. We aimed to study the demographics, clinical characteristics, and outcome of our patients in Sarawak. Materials and methods : This non-interventional, retrospective, and multi-center study was conducted on secondary data of medical records collected at four Sarawak Public Hospitals. All adult myelofibrosis patients diagnosed between January 2001 and December 2021 were included. Results : A total of 63 patients (male 31) with myelofibrosis were included—47 (74.6%) primary and 16 (25.4%) secondary myelofibrosis. Eleven had antecedent polycythaemia vera, whereas five transformed from essential thrombocythaemia. The combined annual incidence rate was 0.182 per 100,000 population. The period prevalence per 100,000 population over the entire study duration was 2.502. The median age was 59.0 years (33.0–93.0). Majority had high-risk (34/63(54.0%)) and intermediate-2 risk disease (19/63(30.2%)). JAK2V617F mutation was identified in 52 patients (82.5%), followed by CALR mutation in 6 (9.5%) and negative for both mutations in 5 (7.9%). Hydroxyurea was used as first-line therapy in 41/63 (65.1%), followed by interferon (8/63(12.7%)) and ruxolitinib (4/63(6.3%)). Out of 46 patients who received second-line therapy, 18 (39.1%) were switched to ruxolitinib and 9 (19.6%) to interferon. The median age of survival for overall patients was 6.8 years. The use of ruxolitinib in myelofibrosis patients showed a better overall 5-year survival compared to the no ruxolitinib arm, despite no statistical significance ( p  = 0.34). Patients who had good performance status had lower hazard of death than patients who had poor performance status (high-risk (95% confidence intervals): 0.06(0.013–0.239), p  < 0.001). Patients with intermediate risk disease had better overall survival compared to those in high-risk group (95% confidence intervals): 0.24(0.082–0.695), p  = 0.009). Conclusion : This registry provides a real-world overview of myelofibrosis patients in our state and highlights the key insight into the unmet clinical need