scholarly journals Lysine catabolism: flow, metabolic role and regulation

2003 ◽  
Vol 15 (1) ◽  
pp. 9-18 ◽  
Author(s):  
Ricardo Francisco Fornazier ◽  
Ricardo Antunes Azevedo ◽  
Renato Rodrigues Ferreira ◽  
Vanderlei Aparecido Varisi
Keyword(s):  
Environmental Changes ◽  
Lysine Biosynthesis ◽  
Direct Result ◽  
Physiological Processes ◽  
Saccharopine Dehydrogenase ◽  
Metabolic Role ◽  
Lysine Concentration ◽  
Lysine Degradation ◽  
Acid Pathway ◽  
Lysine Catabolism

Lysine is an essential amino acid, synthesized in plants in the aspartic acid pathway. The lysine catabolism is performed by the action of two consecutive enzymes, lysine 2-oxoglutarate reductase (LOR) and saccharopine dehydrogenase (SDH). The steady state of lysine is controlled by both, synthesis and catabolism rates, with the final soluble lysine concentration in cereal seeds a direct result of these processes. In the last 40 years, the enzymes involved in lysine biosynthesis have been purified and characterized from some plant species such as carrot, maize, barley, rice, and coix. Recent reports have revealed that lysine degradation might be related to various physiological processes, for instance growth, development and response to environmental changes and stress. The understanding of the regulatory aspects of the lysine biosynthetic and catabolic pathways and manipulation of related enzymes is important for the production of high-lysine plants.

Enzyme Immobilization on Nanomaterials for Biosensor and Biocatalyst in Food and Biomedical Industry

2019 ◽  
Vol 25 (24) ◽  
pp. 2661-2676 ◽  
Author(s):  
Sundaresan Bhavaniramya ◽  
Ramar Vanajothi ◽  
Selvaraju Vishnupriya ◽  
Kumpati Premkumar ◽  
Mohammad S. Al-Aboody ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Enzyme Immobilization ◽  
Food Industry ◽  
Environmental Changes ◽  
Immobilized Enzymes ◽  
Food Industries ◽  
Physiological Processes ◽  
Different Types ◽  
Simple Processing ◽  
Biomedical Industry

Enzymes exhibit a great catalytic activity for several physiological processes. Utilization of immobilized enzymes has a great potential in several food industries due to their excellent functional properties, simple processing and cost effectiveness during the past decades. Though they have several applications, they still exhibit some challenges. To overcome the challenges, nanoparticles with their unique physicochemical properties act as very attractive carriers for enzyme immobilization. The enzyme immobilization method is not only widely used in the food industry but is also a component methodology in the pharmaceutical industry. Compared to the free enzymes, immobilized forms are more robust and resistant to environmental changes. In this method, the mobility of enzymes is artificially restricted to changing their structure and properties. Due to their sensitive nature, the classical immobilization methods are still limited as a result of the reduction of enzyme activity. In order to improve the enzyme activity and their properties, nanomaterials are used as a carrier for enzyme immobilization. Recently, much attention has been directed towards the research on the potentiality of the immobilized enzymes in the food industry. Hence, the present review emphasizes the different types of immobilization methods that is presently used in the food industry and other applications. Various types of nanomaterials such as nanofibers, nanoflowers and magnetic nanoparticles are significantly used as a support material in the immobilization methods. However, several numbers of immobilized enzymes are used in the food industries to improve the processing methods which not only reduce the production cost but also the effluents from the industry.

The catabolic function of the α-aminoadipic acid pathway in plants is associated with unidirectional activity of lysine–oxoglutarate reductase, but not saccharopine dehydrogenase

2000 ◽  
Vol 351 (1) ◽  
pp. 215-220
Author(s):  
Xiaohong ZHU ◽  
Guiliang TANG ◽  
Gad GALILI
Keyword(s):  
Adipic Acid ◽  
Expression System ◽  
Yeast Cells ◽  
Deletion Mutants ◽  
Null Mutant ◽  
Anabolic Activity ◽  
Saccharopine Dehydrogenase ◽  
Intermediate Metabolites ◽  
Acid Pathway ◽  
Transcriptional Controls

Whereas plants and animals use the α-aminoadipic acid pathway to catabolize lysine, yeast and fungi use the very same pathway to synthesize lysine. These two groups of organisms also possess structurally distinct forms of two enzymes in this pathway, namely lysine–oxoglutarate reductase (lysine–ketoglutarate reductase; LKR) and saccharopine dehydrogenase (SDH): in plants and animals these enzymes are linked on to a single bifunctional polypeptide, while in yeast and fungi they exist as separate entities. In addition, yeast LKR and SDH possess bi-directional activities, and their anabolic function is regulated by complex transcriptional and post-transcriptional controls, which apparently ascertain differential accumulation of intermediate metabolites; in plants, the regulation of the catabolic function of these two enzymes is not known. To elucidate the regulation of the catabolic function of plant bifunctional LKR/SDH enzymes, we have used yeast as an expression system to test whether a plant LKR/SDH also possesses bi-directional LKR and SDH activities, similar to the yeast enzymes. The Arabidopsis enzyme complemented a yeast SDH, but not LKR, null mutant. Identical results were obtained when deletion mutants encoding only the LKR or SDH domains of this bifunctional polypeptide were expressed individually in the yeast cells. Moreover, activity assays showed that the Arabidopsis LKR possessed catabolic, but not anabolic, activity, and its uni-directional activity stems from its structure rather than its linkage to SDH. Our results suggest that the uni-directional activity of LKR plays an important role in regulating the catabolic function of the α-amino adipic acid pathway in plants.

scholarly journals Regulation of lysine catabolism through lysine-ketoglutarate reductase and saccharopine dehydrogenase in Arabidopsis.

1997 ◽  
Vol 9 (8) ◽  
pp. 1305-1316 ◽  
Author(s):  
G Tang ◽  
D Miron ◽  
J X Zhu-Shimoni ◽  
G Galili
Keyword(s):  
Saccharopine Dehydrogenase ◽  
Lysine Catabolism

scholarly journals The Activity of theArabidopsisBifunctional Lysine-ketoglutarate Reductase/Saccharopine Dehydrogenase Enzyme of Lysine Catabolism Is Regulated by Functional Interaction between Its Two Enzyme Domains

2002 ◽  
Vol 277 (51) ◽  
pp. 49655-49661 ◽  
Author(s):  
Xiaohong Zhu ◽  
Guiliang Tang ◽  
Gad Galili
Keyword(s):  
Site Directed Mutagenesis ◽  
Functional Interaction ◽  
Linker Region ◽  
Calcium Dependent ◽  
Flight Mass Spectrometry ◽  
Saccharopine Dehydrogenase ◽  
Ef Hand ◽  
Recombinant Polypeptides ◽  
Lysine Catabolism

Lysine-ketoglutarate reductase/saccharopine dehydrogenase (LKR/SDH) is a bifunctional enzyme catalyzing the first two steps of lysine catabolism in animals and plants. To elucidate the biochemical signification of the linkage between the two enzymes of LKR/SDH, namely lysine ketoglutarate and saccharopine dehydrogenase, we employed various truncated and mutatedArabidopsisLKR/SDH polypeptides expressed in yeast. Activity analyses of the different recombinant polypeptides under conditions of varying NaCl levels implied that LKR, but not SDH activity, is regulated by functional interaction between the LKR and SDH domains, which is mediated by the structural conformation of the linker region connecting them. Because LKR activity of plant LKR/SDH enzymes is also regulated by casein kinase 2 phosphorylation, we searched for such potential regulatory phosphorylation sites using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and site-directed mutagenesis. This analysis identified Ser-458 as a candidate for this function. We also tested a hypothesis suggesting that an EF-hand-like sequence at the C-terminal part of the LKR domain functions in a calcium-dependent assembly of LKR/SDH into a homodimer. We found that this region is essential for LKR activity but that it does not control a calcium-dependent assembly of LKR/SDH. The relevance of our results to thein vivofunction of LKR/SDH in lysine catabolism in plants is discussed. In addition, because the linker region between LKR and SDH exists only in plants but not in animal LKR/SDH enzymes, our results suggest that the regulatory properties of LKR/SDH and, hence, the regulation of lysine catabolism are different between plants and animals.

scholarly journals Introduction. Integration of ecology and endocrinology in avian reproduction: a new synthesis

2007 ◽  
Vol 363 (1497) ◽  
pp. 1581-1588 ◽  
Author(s):  
John C Wingfield ◽  
Tony D Williams ◽  
Marcel E Visser
Keyword(s):  
Biological Sciences ◽  
Environmental Changes ◽  
Biological Knowledge ◽  
Avian Reproduction ◽  
Physiological Processes ◽  
Trade Offs ◽  
New Synthesis ◽  
Reproductive Life ◽  
Common Framework ◽  
Collaborative Efforts

Birds are some of the most familiar organisms of global ecosystems. Changes in the visibility and abundance of birds are therefore excellent indicators of population and physiological responses to habitat changes and are a major focus for public concern about detrimental environmental changes. In order to understand how birds respond to these challenges, it is essential to determine how the environment affects reproduction under natural conditions. The continuum from environmental variables (cues) to reproductive life-history traits depends upon a cascade of neural and physiological processes that determine the extent and rate at which birds will be able to adapt to changes in their environment. For a full understanding of this ability to adapt, ecologists and endocrinologists need to collaborate and build a common framework. The objective of this theme issue is to bring together a series of papers addressing how evolutionary ecologists and endocrinologists can collaborate directly using avian reproduction as a model system. First, we address the need to integrate ecology and endocrinology and what benefits to biological knowledge will be gained. The papers collected in this issue represent a new synthesis of ecology and endocrinology as discussed in three E-BIRD workshops. The three main foci are trade-offs and constraints, maternal effects and individual variation. Authors within each group present ecological and endocrinological aspects of their topics and many go on to outline testable hypotheses. Finally, we discuss where the major problems remain and how this issue points out where these need collaborative efforts of ecologists and endocrinologists. Specific challenges are raised to future researchers to break through intellectual barriers and explore new frontiers. This framework of topics will ultimately apply to all taxa because the principles involved are universal and hopefully will have direct application to programmes integrating organisms and genes throughout biological sciences.

scholarly journals Efficiency of Zinc in Plants, its Deficiency and Sensitivity for Different Crops

2021 ◽  
Vol 8 (2) ◽  
pp. 128-134
Author(s):  
Laaraib Tayyiba ◽  
Hooria Zafar ◽  
Aqarab Husnain Gondal ◽  
Qammar Farooq ◽  
Muhammad Muzammil Mukhtar ◽  
...  
Keyword(s):  
Zn Deficiency ◽  
Vegetative Development ◽  
Large Molecules ◽  
Physiological Processes ◽  
Crop Nutrition ◽  
Metabolic Role ◽  
Wide Range ◽  
Physical Functions ◽  
Quality Of Products

Optimal crop nutrition is a significant factor in increasing agricultural vintage and quality of products. Zinc (Zn) is an immobile important micronutrient, which is taken up by plants in Zn2+ form to complete their life cycle efficiently. It plays a critical metabolic role in plants and is an important constituent of proteins and other large-molecules, and serves as structural and functional unit, or controlling cofactor for a wide range of enzymes. The Zn is needed in small and in appropriate amounts for plants main physiological processes to work normally. These processes play critical roles in photosynthetic activity of plants and forming carbohydrates, synthesis of protein, reproduction and seed development, growth, and disease protection. After Zn deficiency in plants, these physical functions are decreased, and plant health and productivity suffer greatly, subsequent in reduced production or even failure of crops and often bad quality of crop products. Plant Zn deficiencies occur on variety of soils and are severe due to a combination of symptoms like chlorosis, resetting, dieback and suppressed or irregular vegetative development. In addition, various crops require varying amount of Zn. So the knowledge regarding this is not up to date. The present review discusses the Zn importance in plants, its deficiency in soil and required level of Zn for crops.

scholarly journals Circadian immune circuits

2020 ◽  
Vol 218 (2) ◽  
Author(s):  
Miguel Palomino-Segura ◽  
Andrés Hidalgo
Keyword(s):  
Immune Responses ◽  
Immune Cells ◽  
Environmental Changes ◽  
Fundamental Property ◽  
Structural Elements ◽  
Host Immune Responses ◽  
Physiological Processes ◽  
Specific Antigens ◽  
Specific Receptors ◽  
Central Clock

Immune responses are gated to protect the host against specific antigens and microbes, a task that is achieved through antigen- and pattern-specific receptors. Less appreciated is that in order to optimize responses and to avoid collateral damage to the host, immune responses must be additionally gated in intensity and time. An evolutionary solution to this challenge is provided by the circadian clock, an ancient time-keeping mechanism that anticipates environmental changes and represents a fundamental property of immunity. Immune responses, however, are not exclusive to immune cells and demand the coordinated action of nonhematopoietic cells interspersed within the architecture of tissues. Here, we review the circadian features of innate immunity as they encompass effector immune cells as well as structural cells that orchestrate their responses in space and time. We finally propose models in which the central clock, structural elements, and immune cells establish multidirectional circadian circuits that may shape the efficacy and strength of immune responses and other physiological processes.

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