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Synthesis, Enzyme Localization, and Regulation of Neurosteroids
Published in Sheryl S. Smith, Neurosteroid Effects in the Central Nervous System, 2003
Zhang, L.H., Rodriguez, H., Ohno, S., and Miller, W.L., Serine phosphorylation of human P450c17 increases 17,20-lyase activity: implications for adrenarche and the polycystic ovary syndrome, Proc. Natl. Acad. Sci. U.S.A., 92, 10619-10623, 1995. Pandey, A.V., Mellon, S.H., and Miller, W.L., Protein phosphatase 2A and phospho-protein SET regulate androgen production by P450c17, J. Biol. Chem., 278,
REGULATORY MECHANISMS
Published in David M. Gibson, Robert A. Harris, Metabolic Regulation in Mammals, 2001
David M. Gibson, Robert A. Harris
Protein degradative pathways in effect are coupled to an«! "pull" on the protein synthetic output. Degradation and synthesis together dcline the homeostatic protein set-point concentrations of the cell, i.e. maintain the phenotypic balance of all proteins that comprise the structures (and thus functions) of the cell. Degradation of most proteins and enzymes is first order, namely protein concentration dependent. In steady-state the synthetic rate of a particular protein equals the rate of degradation, represented by the produci of enzyme concentration, [E| ami a degradative rate constant, k, that is characteristic for the protein substrate in a given cellular proteolytic environment: synthesis = k |F.|. If the synthetic rate is elevated (signaled gene expression) the magnitude of [E] will also rise. Thus the degradative rate rises, to the point where a new steady-state is reached. Consequently the effect of a change in the rate of transcription of a gene is self-limiting w hether it was an increase or a decrease. This also applies to the concentrations ol messenger RNA that ultimately determine the rate of protein synthesis. For example, pyruvate kinase, a cytosolic liver enzyme that converts phosphocnolpvruvatc to pyruvate is one of a set ol enzvmes that is induced by insulin (as seen during I ceding). On the other hand when insulin is low and glucagon elevated (starvation) the enzyme is repressed. Looking at changes in rivo in the course of starvation the diminished rate of transcription is followed in succession by first-order decays in the concentrations of the hn RNA in the nucleus, the niRNA in the nucleus ami the mRNA in the cytosol. Finally the cytosolic enzyme concentration follows its first-order decay curve. As with proteins, the concentration of the several RNA species is a balance between rates of synthesis and first-order decay.
Protein Needs of Athletes
Published in David Lightsey, The Myths about Nutrition Science, 2019
There is no question that the established dietary guidelines for protein set by what are commonly known as the RDAs at 0.8 g/kg/day, are far too low for anyone whose lifestyle requires their body to function beyond its resting metabolic levels. Current evidence indicates that most lifestyles beyond comatose require from 1.2 to 1.6 g/kg/day of high-quality protein per day for optimal health outcomes as well as athletic performance and physical development, and possibly 2.0 g/kg/day for some heavily training athletes. This equates roughly to 20–30 grams of high-quality protein four times per day, and possibly another consumed prior to sleep for some. For an excellent in-depth review of this, the following two reviews published in 2016, in NRC Research Press, “Protein Requirements Beyond the RDA: Implications for Optimizing Health,” and 2018 in Nutrients Review, “Recent Perspectives Regarding the Role of Dietary Protein for the Promotion of Muscle Hypertrophy With Resistance Exercise Training,” are recommended. However, this chapter focuses on two main points: Does this higher intake level require supplemental intervention to be achieved? The answer to this is no, which will be presented, and the recommended levels of intake can be easily achieved using high-quality animal protein sources such as milk, eggs, poultry, meat, etc.What misconceptions do most athletes and active consumers embrace which may lead them to believe they need protein supplemental intervention? There are many. Regarding the first question, consumers and athletes need to keep in mind the points made in Chapter 9 regarding the potential hazards of supplements when considering their sources for protein. Also, Consumerlab.com tests revealed that 20% of the protein supplements they have tested are mislabeled. With those two points in mind consider the cost as well. Consumerlab.com states that to obtain 20 grams of protein from a supplement will range from 80 cents to $1.50. According to the December 24, 2018 USDA Agricultural Marketing Services Dairy Report,1 the average cost of a gallon of milk in the United States is $3.27 for whole milk and $3.21 for 2% milk, both containing 128 grams of protein. So, you can purchase 128 grams of protein from milk for $3.21, without the fear of it being mislabeled or spiked with an unwanted stimulant or steroid, or, you can purchase the equivalent of that 128 grams of protein from the supplement industry from anywhere between $5.12 and $9.60.
Proteomics and plant biology: contributions to date and a look towards the next decade
Published in Expert Review of Proteomics, 2021
Proteomics offers a wide range of techniques and protocols, either wet or dry, whose final result is the identification and quantification of proteins in biological samples, as well as its structural and functional characterization. Those MS-based ones can be classified and categorized in different groups depending on the strategy, including top-down and bottom up, also denominated protein or peptide centric (in the former, intact proteins are analyzed, and in the latter derived peptides, usually after trypsin digestion are), gel- or gel-free (based on the preparative technique employed for protein or protein-derived peptides resolution), label or label free (in which proteins or derived peptides are or not labeled with isotopic or isobaric targets, which determines the protein quantification strategy), holistic (the whole protein set of a cell extract) or hypothesis driven, also named targeted (focus on specific proteins). Methodological aspects of proteomics and its application to plant biology research have been previously reviewed by the author [15–17], with recent reviews also published by Liu et al., 2019 [18], and Smolikova et al. 2020 [19].
Proteomic characterisation of drug metabolising enzymes and drug transporters in pig liver
Published in Xenobiotica, 2020
Yasmine Elmorsi, Hajar Al Feteisi, Zubida M. Al-Majdoub, Jill Barber, Amin Rostami-Hodjegan, Brahim Achour
In proteomics, a variety of sample preparation and quantitative methods have been developed to identify and quantify proteins, and each has its advantages and limitations (Al Feteisi et al., 2015). The strategy adopted in this study used three different sample preparation methods (FASP, eFASP and in-solution) to compare the ability of each to extract liver proteins. Two consecutive steps were followed, identification and relative quantification. The number of identified enzymes and transporters by each of the three methods was comparable for each protein set; 14 CYP and 5 UGT enzymes were identified by each of the three methods, while the number of identified transporters was 10 with FASP and eFASP, and 8 with in-solution sample preparation. This does not necessarily imply that the three methods were always able to isolate the same proteins. In spite of the extensive overlap, different methods tended to identify specific proteins consistently. For example, CYP2C42 and ABCC1 (MRP1) could only be identified when eFASP was used, while CYP3A29 and CYP3A46 were successfully isolated by the two other methods. ABCG2 (BCRP) was consistently isolated by FASP, and the uptake transporter SLCO1B4 (OATP1B4) was not observed with the solution-based protocol. We therefore propose a new definition of replication, for practical purposes, where the same sample is prepared using different protocols, which provide complementary results, and this can then be used to construct a more comprehensive qualitative and quantitative description of the expression patterns of pharmacologically relevant proteins.
Advances in influenza virus-like particles bioprocesses
Published in Expert Review of Vaccines, 2019
Laurent Durous, Manuel Rosa-Calatrava, Emma Petiot
Mass spectrometry analyzes recently demonstrated that both influenza virus and influenza VLPs incorporate a large variety of host cell proteins during their assembly process [39,96,111,112]. Identified proteins are either membrane or cytoplasmic proteins. Unlike for rHA vaccines, the protein set is dependent of the cell platform. These embedded proteins cannot be sorted out during DSP and have to be evaluated for their potential action on the vaccine immunogenicity and reactogenicity. Thus, Novavax demonstrated that baculovirus envelope proteins (gp64 and p39) and Sf9 host cell proteins (tubulin, actin, Hsp70, and several housekeeping proteins) could represent up to 25% of the total protein content of the final vaccine product [113]. The contaminant content of influenza-VLP vaccine candidate produced from plant-based production is much lower (see BOX 1).