Kinetic productivity analysis is critical to the characterization of enzyme catalytic performance... more Kinetic productivity analysis is critical to the characterization of enzyme catalytic performance and capacity. However, productivity analysis has been largely overlooked in the published literature. Less than 0.01% of studies which report on enzyme characterization present productivity analysis, despite the fact that this is the only measurement method that provides a reliable indicator of potential commercial utility. Here, we argue that reporting productivity data involving native, modified, and immobilized enzymes under different reaction conditions will be of immense value in optimizing enzymatic processes, with a view to accelerating biotechnological applications. With the use of examples from wide-ranging studies, we demonstrate that productivity is a measure of critical importance to the translational and commercial use of enzymes and processes that employ them. We conclude the review by suggesting steps to maximize the productivity of enzyme catalyzed reactions.
Nicotinamide adenine dinucleotide (NAD) is an essential pyridine nucleotide that serves as an ele... more Nicotinamide adenine dinucleotide (NAD) is an essential pyridine nucleotide that serves as an electron carrier in cellular metabolism and plays a crucial role in the maintenance of balanced redox homeostasis. Quantification of NAD:NADH and NADP:NADPH ratios are pivotal to a wide variety of cellular processes, including intracellular secondary messenger signaling by CD38 glycohydrolases, DNA repair by poly(adenosine diphosphate ribose) polymerase (PARP), epigenetic regulation of gene expression by NAD-dependent histone deacetylase enzymes known as sirtuins, and regulation of the oxidative pentose phosphate pathway. We quantified changes in the NAD metabolome in plasma samples collected from consenting healthy human subjects across a wide age range (20-87 years) using liquid chromatography coupled to tandem mass spectrometry. Our data show a significant decline in the plasma levels of NAD, NADP, and other important metabolites such as nicotinic acid adenine dinucleotide (NAAD) with ag...
Introduction: Muscle sympathetic nerve activity (MSNA) may play a role in insulin resistance in o... more Introduction: Muscle sympathetic nerve activity (MSNA) may play a role in insulin resistance in obesity. However, the direction and nature of the relationship between MSNA and insulin resistance in obesity remain unclear. We hypothesized that resting MSNA would correlate inversely with both muscle and liver insulin sensitivity and that it would be higher in insulin-resistant vs. insulin-sensitive subjects. Materials and methods: Forty-five non-diabetic obese subjects were studied. As no significant relationships were found in women, the data presented in on 22 men aged 48 ± 12 years. Two-step (15 and 80 mU/m(2)/min) hyperinsulinaemic-euglycaemic clamps were performed using deuterated glucose to determine liver and muscle insulin sensitivity. Clinical and metabolic parameters were assessed. MSNA was measured via a microelectrode inserted percutaneously into the common peroneal nerve. Results: MSNA burst frequency correlated inversely with liver insulin sensitivity (r = -0.53, P = 0.0...
The autosomal dominant form of Alzheimer’s disease (ADAD) is far less prevalent than late onset A... more The autosomal dominant form of Alzheimer’s disease (ADAD) is far less prevalent than late onset Alzheimer’s disease (LOAD), but enables well-informed prospective studies, since symptom onset is near certain and age of onset is predictable. Our aim was to discover plasma proteins associated with early AD pathology by investigating plasma protein changes at the asymptomatic and symptomatic stages of ADAD. Eighty-one proteins were compared across asymptomatic mutation carriers (aMC, n = 15), symptomatic mutation carriers (sMC, n = 8) and related noncarriers (NC, n = 12). Proteins were also tested for associations with cognitive measures, brain amyloid deposition and glucose metabolism. Fewer changes were observed at the asymptomatic than symptomatic stage with seven and 16 proteins altered significantly in aMC and sMC, respectively. This included complement components C3, C5, C6, apolipoproteins A-I, A-IV, C-I and M, histidine-rich glycoprotein, heparin cofactor II and attractin, which...
Alzheimer's disease (AD) is a neurodegenerative disorder associated with increased oxidative ... more Alzheimer's disease (AD) is a neurodegenerative disorder associated with increased oxidative stress and neuroinflammation. Markers of increased protein, lipid and nucleic acid oxidation and reduced activities of antioxidant enzymes have been reported in AD plasma. Amyloid plaques in the AD brain elicit a range of reactive inflammatory responses including complement activation and acute phase reactions, which may also be reflected in plasma. Previous studies have shown that human AD plasma may be cytotoxic to cultured cells. We investigated the effect of pooled plasma (n = 20 each) from healthy controls, individuals with amnestic mild cognitive impairment (aMCI) and Alzheimer's disease (AD) on cultured microglial cells. AD plasma and was found to significantly decrease cell viability and increase glycolytic flux in microglia compared to plasma from healthy controls. This effect was prevented by the heat inactivation of complement. Proteomic methods and isobaric tags (iTRAQ) f...
Alzheimer&amp... more Alzheimer's disease is a complex multifactorial age-related neurodegenerative disorder. Current transgenic animal models do not fully recapitulate human Alzheimer's disease at the molecular, cellular and behavioural levels. This review aims to address the clinical relevance of using 'physiologically' aged rats, dogs and Octodon degus, as more representative 'natural' ecologically valid models to elucidate mechanistic aspects of Alzheimer's disease, and for the development of therapeutic agents to attenuate age-related cognitive decline. Aged rats, dogs and O. degus decline cognitively and ultimately develop Alzheimer's disease-like symptoms in response to the natural ageing process. Aged rats provide a tractable and popular model to examine the neurobiological basis underlying cognitive decline with age, but they do not develop Alzheimer's disease pathology. Progressive accumulation of abnormal amyloid-beta in extracellular plaques and surrounding cerebral vasculature is a common feature in human Alzheimer's disease, aged canine model and most nonhuman primates. Interestingly, the O. degus develops amyloid-beta deposits, neurofibrillary tangles containing hyperphosphorylated tau protein, altered cholinergic transmission and cognitive deficits analogous to those observed in…
Glutamate was identified as the main excitatory neurotransmitter in the mammalian central nervous... more Glutamate was identified as the main excitatory neurotransmitter in the mammalian central nervous system (CNS) following the observation in the early 1950s that glutamate can induce seizure activity and excite neurons in the mammalian brain. Over the last two decades, selective ligands, including competitive agonists and antagonists and allosteric modulators, have been developed to further investigate the functional role of glutaminergic receptors. Glutamate released from synapses can activate ligand-gated cation channels at postsynaptic cells to mediate fast postsynaptic potentials. These ion channel-forming ionotropic glutamate receptors (iGluRs) are divided into N-methyl-D-aspartate (NMDA), α-amino-3-hydroxyl-5-methyl-isoxazole-4-prorionate (AMPA), and kainate (KA) receptors. While only 20–30 % of the amino acid sequence is shared among these receptor subtypes, they share similar structural features and their activity is based on specific pharmacological preference. In this chapter, we will describe the structure and composition of iGluRs and infer their pharmacology, with a particular focus on their role in the CNS and their relevance to the pathogenesis of neurodegenerative diseases.22 page(s
Kinetic productivity analysis is critical to the characterization of enzyme catalytic performance... more Kinetic productivity analysis is critical to the characterization of enzyme catalytic performance and capacity. However, productivity analysis has been largely overlooked in the published literature. Less than 0.01% of studies which report on enzyme characterization present productivity analysis, despite the fact that this is the only measurement method that provides a reliable indicator of potential commercial utility. Here, we argue that reporting productivity data involving native, modified, and immobilized enzymes under different reaction conditions will be of immense value in optimizing enzymatic processes, with a view to accelerating biotechnological applications. With the use of examples from wide-ranging studies, we demonstrate that productivity is a measure of critical importance to the translational and commercial use of enzymes and processes that employ them. We conclude the review by suggesting steps to maximize the productivity of enzyme catalyzed reactions.
Nicotinamide adenine dinucleotide (NAD) is an essential pyridine nucleotide that serves as an ele... more Nicotinamide adenine dinucleotide (NAD) is an essential pyridine nucleotide that serves as an electron carrier in cellular metabolism and plays a crucial role in the maintenance of balanced redox homeostasis. Quantification of NAD:NADH and NADP:NADPH ratios are pivotal to a wide variety of cellular processes, including intracellular secondary messenger signaling by CD38 glycohydrolases, DNA repair by poly(adenosine diphosphate ribose) polymerase (PARP), epigenetic regulation of gene expression by NAD-dependent histone deacetylase enzymes known as sirtuins, and regulation of the oxidative pentose phosphate pathway. We quantified changes in the NAD metabolome in plasma samples collected from consenting healthy human subjects across a wide age range (20-87 years) using liquid chromatography coupled to tandem mass spectrometry. Our data show a significant decline in the plasma levels of NAD, NADP, and other important metabolites such as nicotinic acid adenine dinucleotide (NAAD) with ag...
Introduction: Muscle sympathetic nerve activity (MSNA) may play a role in insulin resistance in o... more Introduction: Muscle sympathetic nerve activity (MSNA) may play a role in insulin resistance in obesity. However, the direction and nature of the relationship between MSNA and insulin resistance in obesity remain unclear. We hypothesized that resting MSNA would correlate inversely with both muscle and liver insulin sensitivity and that it would be higher in insulin-resistant vs. insulin-sensitive subjects. Materials and methods: Forty-five non-diabetic obese subjects were studied. As no significant relationships were found in women, the data presented in on 22 men aged 48 ± 12 years. Two-step (15 and 80 mU/m(2)/min) hyperinsulinaemic-euglycaemic clamps were performed using deuterated glucose to determine liver and muscle insulin sensitivity. Clinical and metabolic parameters were assessed. MSNA was measured via a microelectrode inserted percutaneously into the common peroneal nerve. Results: MSNA burst frequency correlated inversely with liver insulin sensitivity (r = -0.53, P = 0.0...
The autosomal dominant form of Alzheimer’s disease (ADAD) is far less prevalent than late onset A... more The autosomal dominant form of Alzheimer’s disease (ADAD) is far less prevalent than late onset Alzheimer’s disease (LOAD), but enables well-informed prospective studies, since symptom onset is near certain and age of onset is predictable. Our aim was to discover plasma proteins associated with early AD pathology by investigating plasma protein changes at the asymptomatic and symptomatic stages of ADAD. Eighty-one proteins were compared across asymptomatic mutation carriers (aMC, n = 15), symptomatic mutation carriers (sMC, n = 8) and related noncarriers (NC, n = 12). Proteins were also tested for associations with cognitive measures, brain amyloid deposition and glucose metabolism. Fewer changes were observed at the asymptomatic than symptomatic stage with seven and 16 proteins altered significantly in aMC and sMC, respectively. This included complement components C3, C5, C6, apolipoproteins A-I, A-IV, C-I and M, histidine-rich glycoprotein, heparin cofactor II and attractin, which...
Alzheimer's disease (AD) is a neurodegenerative disorder associated with increased oxidative ... more Alzheimer's disease (AD) is a neurodegenerative disorder associated with increased oxidative stress and neuroinflammation. Markers of increased protein, lipid and nucleic acid oxidation and reduced activities of antioxidant enzymes have been reported in AD plasma. Amyloid plaques in the AD brain elicit a range of reactive inflammatory responses including complement activation and acute phase reactions, which may also be reflected in plasma. Previous studies have shown that human AD plasma may be cytotoxic to cultured cells. We investigated the effect of pooled plasma (n = 20 each) from healthy controls, individuals with amnestic mild cognitive impairment (aMCI) and Alzheimer's disease (AD) on cultured microglial cells. AD plasma and was found to significantly decrease cell viability and increase glycolytic flux in microglia compared to plasma from healthy controls. This effect was prevented by the heat inactivation of complement. Proteomic methods and isobaric tags (iTRAQ) f...
Alzheimer&amp... more Alzheimer's disease is a complex multifactorial age-related neurodegenerative disorder. Current transgenic animal models do not fully recapitulate human Alzheimer's disease at the molecular, cellular and behavioural levels. This review aims to address the clinical relevance of using 'physiologically' aged rats, dogs and Octodon degus, as more representative 'natural' ecologically valid models to elucidate mechanistic aspects of Alzheimer's disease, and for the development of therapeutic agents to attenuate age-related cognitive decline. Aged rats, dogs and O. degus decline cognitively and ultimately develop Alzheimer's disease-like symptoms in response to the natural ageing process. Aged rats provide a tractable and popular model to examine the neurobiological basis underlying cognitive decline with age, but they do not develop Alzheimer's disease pathology. Progressive accumulation of abnormal amyloid-beta in extracellular plaques and surrounding cerebral vasculature is a common feature in human Alzheimer's disease, aged canine model and most nonhuman primates. Interestingly, the O. degus develops amyloid-beta deposits, neurofibrillary tangles containing hyperphosphorylated tau protein, altered cholinergic transmission and cognitive deficits analogous to those observed in…
Glutamate was identified as the main excitatory neurotransmitter in the mammalian central nervous... more Glutamate was identified as the main excitatory neurotransmitter in the mammalian central nervous system (CNS) following the observation in the early 1950s that glutamate can induce seizure activity and excite neurons in the mammalian brain. Over the last two decades, selective ligands, including competitive agonists and antagonists and allosteric modulators, have been developed to further investigate the functional role of glutaminergic receptors. Glutamate released from synapses can activate ligand-gated cation channels at postsynaptic cells to mediate fast postsynaptic potentials. These ion channel-forming ionotropic glutamate receptors (iGluRs) are divided into N-methyl-D-aspartate (NMDA), α-amino-3-hydroxyl-5-methyl-isoxazole-4-prorionate (AMPA), and kainate (KA) receptors. While only 20–30 % of the amino acid sequence is shared among these receptor subtypes, they share similar structural features and their activity is based on specific pharmacological preference. In this chapter, we will describe the structure and composition of iGluRs and infer their pharmacology, with a particular focus on their role in the CNS and their relevance to the pathogenesis of neurodegenerative diseases.22 page(s
Uploads
Papers