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Results for “functional amino acids”

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At least 19 recordsLinked to original sources
PubMed1978

Identification of the amino acid functional groups responsible for 30-S ribosome recognition of messenger RNA.

About 30 protein-selective chemical reagents have been tested for their ability to inhibit the mRNA binding activity of the 30-S ribosome. A number of reagents were investigated which have been shown by other workers to be capable of modifying free epsilon-amino groups of lysine and all were found to inactivate 30-S ribosomes completely for natural mRNA binding activity. Several reagents selective for histidine, tyrosine, and tryptophan were also found to inactivate. We suggest that the epsilon-amino groups of lysine play an important role in mRNA binding to the 30-S ribosome.

Amines↗
PubMed1979

Biomolecules bearing the S- or SeAsMe2 function: amino acid and steroid derivatives.

A series of molecules of the type GXAsMe2 have been synthesized in which X is S or Se and G is a moiety such as an amino acid, a di- or tripeptide, or a lipid. The compounds have been characterized by NMR, mass spectroscopy, and elemental analysis. Cysteine was found to react directly with dimethylarsinic acid to yield cystine and S-dimethylarsinocysteine (1). This reaction occurs also with other biomolecules containing thiol groups and raises serious questions concerning the use of cacodylate buffers in the study of enzyme kinetics and in sample preparation for electron microscopy. In the presence of dimethylchloroarsine and diethylamine, homocysteine thiolactone reacts to form both the dipeptide and the S-AsMe2 bond. Results of carcinostatic, bacteriostatic, and fungicidal testing of these compounds are reported. A hypothesis is advanced to explain the observed carcinostatic action of the dimethylarsino group.

Amino Acids↗
PubMed1979

Methionine transport in S37 cells. Substrate-dependent function of amino acid transport system A in exchange processes.

Methionine had been observed to interact with two principal transport systems for amino acids in mammalian cells, the A and L systems. The present study of methionine transport and of exchange processes through system A arose in the course of a study to define the specificity of a transinhibition effect caused by cysteine. Methionine uptake through two transport systems in the S37 cell was confirmed by the occurrence of a biphasic double-reciprocal plot for labeled methionine uptake. Preloading cells with methionine stimulated labeled histidine uptake through systems A and L. Efflux of labeled methionine from cells was stimulated by histidine in a biphasic manner, so that bothe systems A and L can be used for exchange when methionine is the intracellular amino acid. Aminocycloheptanecarboxylic acid elicited exchange efflux of labeled methionine only through system L. ALPHA-Aminoisobutyric acid and N-methyl-alpha-aminoisobutyric acid both stimulated efflux of labeled N-methyl-alpha-aminoisobutyric acid from S37 cells. These findings are interpreted a showing that transport system A is capable of functioning as an exchange system depending upon the identity of intracellular and extracellular substrates available.

Amino Acids↗
PubMed1975

Rates of protein evolution: a function of amino acid composition.

Conservation of secondary and tertiary structure in proteins suggests that rates of sequence variation reflect differences in the total number of amino acid replacements that are compatible with preservation of structure. Consequently, rates of sequence variation depend on whether the constituent amino acids of individual proteins are, over-all, more subject or less subject to evolutionary substitution than normal. Such rates correlate well with a mutability term based on amino acid composition.

Amino Acid Sequence↗
PubMed1979

Effects of eight amino acids on the exocrine and endocrine pancreatic function.

Eight amino acids were intravenously administered in a dose of 2 mmoles/kg/hr to dogs with chronic pancreatic fistula, and the effect of each amino acid on endocrine and exocrine pancreatic secretions was investigated. Asparagine, arginine, isoleucine and phenylalanine administered under the stimulation of secretin-pancreozymin significantly inhibited the secretion of pancreatic juice by 23%, 15%, 13% and 13%, and the output of amylase by 53%, 37%, 27% and 18%, respectively. Threonine, glycine or methionine brought about no significant changes in pancreatic secretion, but valine significantly increased pancreatic juice secretion by 13% and amylase output by 15%. Any of the eight amino acids caused no noticeable change in the concentration of bicarbonate.

Amino Acids↗
PubMedDate not supplied

The renal effect of intravenous adenine in humans.

The purine base, adenine, improves the posttransfusion viability of liquid stored blood. However, adenine in high doses may cause kidney damage becuase of the precipitation in renal tubules of its incoluble metabolite, 2,8-dioxyadenine. Adenine is not licensed for use in the United States because it may be nephrotoxic. In a controlled, randomized, double-blind study, eight human subjects received 10 mg/kg of adenine infused intravenously over one hour, four subjects received 5 mg/kg, and four subjects received no adenine. Renal function tests were performed on each subject before adenine infusion and one day and one week following the infusion. Tests included an assessment of glomerular function (serum creatinine, creatinine clearance, protein excretion), proximal tubular function (amino acid and glucose excretion), and distal tubular function (maximal acidifying and concentrating ability). Plasma and urine levels of adenine and 2,8-dioxyadenine were measured. Renal function tests showed no evidence of kidney damage secondary to adenine.

Adenine↗
PubMedDate not supplied

[Denaturation temperature of collagen as a linear function of its amino acid composition].

TD of collagen have been constructed as linear function of fractions of each from 18 amino acids using experimental data for 29 proteins. For coefficient estimation the least squire method have been used. As a result the TD of any collagen may be calculated by using of the function obtained. 14 amino acids strongly influence on TD. The suggestion arises that poly(Gly-Ile-Lys) may produce collagen like structure.

Amino Acids↗
PubMed1978

The effects of bioregulators upon amino acid transport and protein synthesis in isolated rat hepatocytes.

Isolated rat hepatocytes prepared by an enzyme perfusion technique possess a functional amino acid transport system and retain the capacity to synthesize protein. Amino acid transport was studied using the non-metabolizable amino acid analog alpha-aminoisobutyric acid. The transport process was time, temperature and concentration dependent. Similarly, leucine incorporation into protein was time and temperature dependent being optimal at 3m degrees C. Amino acid, fetal calf serum, growth hormone and glucose all produced small, reproducible increases in protein synthesis rates. Bovine serum albumin diminished the uptake of alpha-aminoisobutyric acid and leucine incorporation into protein. The amino acid content on either side of the cell membrane was found to affect transport into or out of the cellular compartment (transconcentration effects). High cell concentrations decreased transport and protein synthesis as a result of isotopic dilution of labelled amino acids with those released by the hepatocytes. This was consistent with the capacity of naturally occurring amino aicds to compete with alpha-aminoisobutyric acid for uptake into the hepatocyte. In order to define more precisely the effects of bioregulators on transport and protein synthesis it will be necessary to define and subfractionate cellular compartments and proteins which are the specific targets of cellular regulation.

Amino Acids↗
PubMed1975

Human anaphylatoxin (C3a) from the third component of complement. Primary structure.

C3a anaphylatoxin is derived from the third component (C3) of the blood complement system. Selective proteolysis of C3 by activated proenzymes indigenous to blood generates the C3a fragment. Human C3a was isolated from inulin-activated serum containing 6-aminohexanoic acid, according to recently published procedures (Hugli, T. E., Vallota, E., and Müller-Eberhard, H. J. (1975) J. Biol. Chem. 250, 1472-1498). The human C3a fragment is a highly cationic molecule exhibiting an approximate molecular weight of 9000 and composed of 77 amino acid residues. It consists of a single polypeptide chain containing 8% cysteine and lacks both tryptophan and carbohydrate. A tentative primary structure for the human C3a molecule, deduced from overlapping peptides obtained after cyanogen bromide cleavage, tryptic and chymotryptic digestion, is: See article. Two cystelhylcysteine sequences were established at positions 22, 23 and 56, 57 in human C3a. The 6 half-cystine residues in C3a are all interconnected through three disulfide linkages intersecting in a disulfide knot. The functionally amino acid residues distributed among 14 residues at the COOH-terminal end of C3a. This unusually cationic COOH-terminal region of C3a is presumed to play an important role in the interaction of this protein molecule with cellular receptors. A comparison between the linear sequence of human C3a and the NH2-terminal sequences of light and heavy chains of human immunoglobulin indicates that limited identity exists.

Amino Acid Sequence↗
PubMed2026

Phosphorus modulates starch granule development and metabolic partitioning in wheat grain: Insights from SGAP proteomics and nutrition and processing quality.

This study investigates how phosphorus (P) levels are associated with carbon-nitrogen metabolism in wheat grains. Optimal P application (105 kg P₂O₅ ha⁻¹) was associated with enhanced pericarp-endosperm coordination, increased carbon allocation to the endosperm, and early B‑type starch granule formation. Starch granule‑associated protein (SGAP) proteomics showed that optimal P upregulated cytoskeletal and starch‑synthesis proteins bound to starch granules in the endosperm, while reducing storage protein degradation‑related SGAPs in the pericarp. These metabolic adjustments were correlated with increased grain‑filling intensity and duration, and were associated with the highest theoretical grain weight (50.70 mg). Furthermore, optimal P was associated with enrichment of amino acid biosynthesis pathways and with higher levels of essential amino acids (e.g., lysine and threonine by 17.0--26.8%) and an improved essential amino acid profile without altering total protein content. In contrast, excessive P (210 kg P₂O₅ ha⁻¹) was associated with disrupted inter‑tissue coordination but did not simply impair grain filling; instead, HP corresponded to a unique developmental program: it was linked to an early burst of C‑type starch granules (0∼5 µm) at 7 DPA, yet by maturity achieved the highest proportion of large A‑type granules (56.8%) and the highest total starch content (63.5%), together with elevated endosperm phosphorus at 14 DPA and enrichment of spliceosome‑related pathways. HP also showed higher levels of several functional amino acids (glutamate, cysteine, histidine, proline) compared to P0. However, HP was associated with a higher gliadin/globulin ratio and did not improve grain yield. These findings suggest that phosphorus supply is associated with grain quality through tissue‑specific metabolic reprogramming, and that precision management-rather than maximized application-warrants consideration for optimizing both yield and processing quality.

Triticum↗
PubMed1978

Functional tyrosyl residues of carboxypeptidase A. The effect of protein structure on the reactivity of tyrosine-198.

Coupling of bovine carboxypeptidase A with diazotized 5-amino-1H-tetrazole increases esterase activity, decreases peptidase activity slightly, and modifies one tyrosyl residue. Subsequent nitration of the azoenzyme has no further effect on esterase activity, decreases peptidase activity markedly, and modifies a second tyrosyl residue. Analysis of the azopeptides isolated from a chymotrypsin digest of the doubly modified enzyme by affinity, ion exchange, and high pressure liquid chromatography indicates that the principal residue modified by diazo-1H-tetrazole is Tyr-248. Analysis of the nitropeptides isolated by similar procedures indicates that nitration occurs mainly at Tyr-198. This residue becomes susceptible to modification only as a consequence of a conformational change that accompanies azo coupling of Tyr-248. These results describe a unique example of the influence of protein structure on the reactivity of functional amino acid residues and illustrate an important aspect of chemical modification of enzymes.

Amino Acids↗
PubMed1976

Amino-acid pool composition of Saccharomyces cerevisiae as a function of growth rate and amino-acid nitrogen source.

The composition of the amino-acid pool of Saccharomyces cerevisiae is markedly influenced by the amino-acid nitrogen source. The yeast tends to accumulate the amino acid supplied and those closely related to it metabolically. A relatively high concentration of glutamic acid is maintained in the pools of all cultures irrespective of the nitrogen source, reflecting the central role of glutamic acid in nitrogen metabolism. The total amino-acid pool concentration increases as a function of growth rate, although differences exist in the behaviour of individual amino acids.

Amino Acids↗
PubMed1976

[Constant level of intestinal amino acids as a function of the composition of same].

The present study was conducted with pigs. It was designed to investigate whether extreme amino acid proportions in the ration would influence the excretion of endogenic amino acids in the faeces. Addition of DL-methionine or L-Lysine produced slight changes in the composition of endogenic intestiornal protein, a fact that was practically of little or no importance for the method of faecal analysis used in determining the true digestibility of amino acids (classical technique).

Amino Acids↗
PubMed1978

Effects of hypertonic glucose and amino acid infusions on pancreatic exocrine function.

Inhibiting effects of hypertonic glucose and amino-acids on pancreatic exocrine function were studied using mongrel dogs with chronic gastric and pancreatic fistulae. Under the basal stimulation with secretin and pancreoxymin, 20% glucose, 30% glucose and 12% amino acids were given intravenously. Infusion of these substances caused the maximal decreases in pancreatic juice volume and amylase output, to 23% and 11%, respectively (20% glucose), 32% and 29% (30% glucose), and 53% and 42% (12% amino acids). But no significant changes were noted in bicarbonate concentration. When glucose was infused, the rise in levels of blood sugar and IRI was associated with the inhibition of pancreatic exocrine secretion. Aminoacid infusion produced the greatest inhibitory effect on the pancreatic secretion and markedly elevated both the levels of IRI and IRG. Intravenous infusion of glucagon suppressed notably the exocrine function of the pancreas.

Amino Acids↗