8/10/2023 0 Comments Protein turnover![]() Protein synthesis rates are high in the premature newborn, possibly about 11–14 g protein synthesized per kilogram of body weight per day, and these rates decline with growth and development so that in term babies and young adults these rates are about 7 g andįigure 4.6 The two endogenous nitrogen cycles that determine the status of body protein (nitrogen) balance. In the adult these two cycles operate so that they are effectively in balance (nitrogen intake = nitrogen excretion and protein synthesis = protein break-down), but the intensity of the two cycles differs, the flow of nitrogen (and amino acids) being about three times greater for the protein synthesis/breakdown component than for nitrogen intake/excretion cycle. the balance between protein synthesis and break-down (Figure 4.6).the balance between intake and excretion.In effect, there are two endogenous nitrogen cycles that determine the status of balance in body protein: Changes in the rates and efficiencies of one or more of these systems lead to an adjustment in whole body nitrogen (protein) balance and retention, with the net direc-tion and the extent of the balance depending upon the sum of the interactions occurring among the pre-vailing factor(s). This will be a topic for discussion in the following volume. Other factors, including hormones and immune system products, also regulate these systems. TNF, tumor necro-sis factor, IL, interleukin.ĭietary and nutritional factors determine, in part, the dynamic status of these systems such factors include the dietary intake levels relative to the host’s protein and amino acid requirements, the form and route of delivery of nutrients, i.e., parenteral (venous) and enteral (oral) nutritional support, and timing of intake during the day, especially in relation to the intake of the major energy-yielding substrates, which are the carbohydrates and fats in foods. amino acid synthesis, in the case of the nutritionally dispensable or conditionally indispensable amino acids.įigure 4.5 The major systems in amino acid uptake, utilization, and catabolism, with an indication of the processes involved and some factors that can affect them.amino acid interconversions, transformation, and eventually oxidation, with elimination of carbon dioxide and urea production.The principal metabolic systems responsible for the maintenance of body protein and amino acid homeo-stasis are shown in Figure 4.5. Protein synthesis, degradation, and turnover DELTA enables studies of adaptive and maladaptive plasticity in brain-wide neural circuits.Turnover of proteins and amino acid metabolism A novel variant of expansion microscopy further facilitated turnover measurements at individual synapses. The synaptic protein PSD95 was destabilized in specific brain regions by behavioral enrichment. The nuclear protein MeCP2 showed brain region- and cell type-specific turnover. DELTA relies on rapid covalent capture by HaloTag of fluorophores that were optimized for bioavailability in vivo. We describe a pulse-chase method (DELTA) for measuring protein turnover with high spatial and temporal resolution throughout the body, including the brain. Current methods for tracking protein turnover lack the spatial and temporal resolution needed to investigate these processes, especially in the intact brain, which presents unique challenges. ![]() This turnover ranges from minutes to weeks, as it varies across proteins, cellular compartments, cell types, and tissues. Cells regulate function by synthesizing and degrading proteins. ![]()
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