Search results for "arginine"
showing 10 items of 389 documents
Membrane Transport of l-Arginine and Cationic Amino Acid Analogs
2000
Publisher Summary This chapter reviews the current knowledge of the mechanisms and regulation of cationic amino acids (CAA) carrier proteins and discusses the potential involvement of each transporter in supplying L-arginine for nitric oxide biosynthesis. The CAA L-arginine, the substrate for nitric oxide synthases (NOSs), is considered a semi-essential amino acid in most mammals. Consequently, mammalian cells must be capable of exchanging CAA with the environment. The bilayer of the plasma membrane is impermeable to polar molecules, and thus, specialized carrier proteins with distinct substrate specificity transport hydrophilic solutes such as amino acids. L-arginine shares the same transp…
Mathematic predictive models for calculating copper, iron and zinc dialysability in infant formulas
2001
Differences in the dialysability of a mineral element from infant formulas of the same type were detected in a previous study. As these may be due to the effects that different levels of the components of the formulas could have on dialysability, we attempted to establish mathematical models to predict the dialysability of Cu, Fe and Zn from infant formulas according to their ascorbic, citric, or selected amino acid contents. A simple linear regression was applied between the ascorbic acid, citric acid and amino acid contents and the Cu, Fe and Zn dialysability of 18 powdered infant formulas of different types. Significant correlations (P<0.05) were obtained between the dialysability of Fe …
Contents of free amino acids in needles of Norway Spruce trees in relation to novel forest decline. Studies on trees from a site in the northern Blac…
1993
The free amino acid content in needles of Norway spruce trees (about 45-year-old) was determined by means of HPLC. The studied trees have been growing at a forestry site in the Black Forest which is characterized by a high impact of ozone and magnesium deficiency. Measurements were carried out on visibly healthy and on damaged trees on several dates during two vegetation periods and during the course of a day. The amino acids occurring at the highest concentrations were glutamate, arginine, aspartate, and glutamine. The typical seasonal changes in the content of free amino acids, with their minimum during summer, were disturbed in the needles of the damaged trees. Particularly in summer and…
Seasonal-variation of nitrogenous compounds in the xylem sap of citrus
1983
Samples of tracheal sap of Citrus sinensis (L.) Osbeck cv. Washington Navel were taken from field trees throughout the year and the nitrogen composition of the sap was determined. The nitrogenous fraction of the sap was composed mainly of free amino acids (92–97% of total nitrogen) and nitrates throughout the year. Proline was the most abundant amino acid during almost the entire cycle, and its concentration was especially high during the autumn and winter period. Nevertheless, a significant part (40–60%) of the total organic nitrogen was transported as arginine. Total nitrogen as well as amino acids and nitrates were maximal at spring flush. At spring flush and summer flush there was also …
Transport-related amino acid metabolism in germinating barley grains
1987
When eight [14C]-labelled amino acids were separately injected into the endosperm of germinating (4 days at 20°C) barley (Hordeum vulgare L. cv. Himalaya) grains, the label was rapidly taken up by the scutellum and further transported to the shoot and roots. Some of the amino acids (leucine, lysine and asparagine) were transported in an intact form through the scutellum to the seedling, whilst glutamic acid and aspartic acid were largely converted to glutamine in the scutellum. Proline was mainly transported unchanged, but a small part of the label appeared in glutamine. Arginine was mostly broken down in the scutellum, possibly providing ammonia for the synthesis of glutamine. During furth…
Designed peptides for biomineral polymorph recognition: a case study for calcium carbonate
2020
With their unique ability for substrate recognition and their sequence-specific self-assembly properties, peptides play an important role in controlling the mineralization of inorganic materials in natural systems and in controlling the assembly of soft materials into complex structures required for biological functions. Here we report the use of an engineered heptapeptide that can differentiate between the crystalline anhydrous polymorphs of calcium carbonate. This peptide contains the positively charged amino acid arginine as well as proline rather than the prototypical negatively charged aspartate or glutamate units. Its affinity to vaterite compared to aragonite was demonstrated by fluo…
RP-HPLC Determination of Tiger Nut and Orgeat Amino Acid Contents
2005
The amino acid profile of 11 samples of tiger nuts ( Cyperus esculentusL.) grown in the area of “L'Horta Nord” in Valencia (Spain) and one sample of African origin were determined, along with the amino acid contents of 10 samples of natural orgeat from Valencia. Protein was hydrolysed by hydrochloric acid at 110 °C for 23 h, and amino acids were derivatised with AQC and determined by RP-HPLC with fluorescence detection. The chromatographic conditions were optimised. The analytical parameters (detection and quantification limits, precision and accuracy) showed the method to be sufficiently sensitive and reproducible for determining amino acids resistant to acid hydrolysis in tiger nuts and o…
Plasma membrane transporters for arginine
2004
The supply of arginine may become rate limiting for enzymatic reactions that use this semiessential amino acid as a substrate (e.g., nitric oxide, agmatine, creatine, and urea synthesis), particularly under conditions of high demand such as growth, sepsis, or wound healing. In addition, arginine acts as a signaling molecule that regulates essential cellular functions such as protein synthesis, apoptosis, and growth. In the past decade, a number of carrier proteins for amino acids have been identified on the molecular level. They belong to different gene families, exhibit overlapping but distinctive substrate specificities, and can further be distinguished by their requirement for the cotran…
REGULATION OF CATIONIC AMINO ACID TRANSPORT: The Story of the CAT-1 Transporter
2004
▪ Abstract The discovery of the function of the receptor for the ecotropic retrovirus as a membrane transporter for the essential amino acids lysine and arginine was a landmark finding in the field of molecular nutrition. This finding indicated that cationic amino acid transporters (CATs) act pathologically as viral receptors. The importance of this transporter was further supported by knockout mice that were not viable after birth. CAT-1 was the first amino acid transporter to be cloned; several other CATs were later characterized biochemically and molecularly. These transporters mediate the bidirectional transport of cationic amino acids, thus supporting important metabolic functions, s…
Two proteases from nuclei of rat testis cells. I. Isolation
1987
Abstract Two proteases, assayed with fluorogenic peptides and tentatively designated Rc and Kc, have been isolated from nuclei of rat testis cells by differential extraction with acetic acid, removal of some proteins at pH 4.5, and polyacrylamide gel electrophoresis followed by electroblotting onto nitrocellulose paper. Protease R hydrolyzes t‐Butyl‐oxycarbonyl‐Val‐Pro‐Arg‐7‐amino‐4‐methyl‐coumarin and other peptides in which arginine is joined to 7‐amino‐4‐methyl‐coumarin by amide linkage. Protease Kc has a preference for peptides terminating in lysine‐7‐amino‐4‐methylcoumarin amide. Neither of these proteases is active against Glu‐Phe‐7‐amino‐4‐methyl‐coumarin amide or Carbobenzoxy‐Arg‐7‐…