Characterization of transient species in laser photolysis of aromatic amino acids using acetone as photosensitizer

1999 ◽  
Vol 42 (6) ◽  
pp. 561-566 ◽  
Author(s):  
Qinhua Song ◽  
Yeping Xu ◽  
Shuqin Yu ◽  
Congxiang Chen ◽  
Xingxiao Ma ◽  
...  
Keyword(s):  
Amino Acids ◽  
Aromatic Amino Acids ◽  
Laser Photolysis ◽  
Transient Species

Characterization of an isozyme of S-adenosylmethionine synthetase from rat liver

1984 ◽  
Vol 62 (5) ◽  
pp. 276-279 ◽  
Author(s):  
C. H. Lin ◽  
W. Chung ◽  
K. P. Strickland ◽  
A. J. Hudson
Keyword(s):  
Amino Acids ◽  
Molecular Weight ◽  
Amino Acid ◽  
Enzymatic Synthesis ◽  
Gel Filtration ◽  
Deae Cellulose ◽  
Aromatic Amino Acids ◽  
Adenosylmethionine Synthetase ◽  
Cellulose Column

An isozyme of S-adenosylmethionine synthetase has been purified to homogeneity by ammonium sulfate fractionation, DEAE-cellulose column chromatography, and gel filtration on a Sephadex G-200 column. The purified enzyme is very unstable and has a molecular weight of 120 000 consisting of two identical subunits. Amino acid analysis on the purified enzyme showed glycine, glutamate, and aspartate to be the most abundant and the aromatic amino acids to be the least abundant. It possesses tripolyphosphatase activity which can be stimulated five to six times by S-adenosylmethionine (20–40 μM). The findings support the conclusion that an enzyme-bound tripolyphosphate is an obligatory intermediate in the enzymatic synthesis of S-adenosylmethionine from ATP and methionine.

scholarly journals Identification of the Tyrosine- and Phenylalanine-Derived Soluble Metabolomes of Sorghum

2021 ◽  
Vol 12 ◽  
Author(s):  
Jeffrey P. Simpson ◽  
Jacob Olson ◽  
Brian Dilkes ◽  
Clint Chapple
Keyword(s):  
Amino Acids ◽  
Cinnamic Acid ◽  
Aromatic Amino Acids ◽  
Flavonoid Glycosides ◽  
Coumaric Acid ◽  
Biotic And Abiotic Stress ◽  
Proportional Contribution ◽  
Negative Ionization ◽  
Derivatives Of

The synthesis of small organic molecules, known as specialized or secondary metabolites, is one mechanism by which plants resist and tolerate biotic and abiotic stress. Many specialized metabolites are derived from the aromatic amino acids phenylalanine (Phe) and tyrosine (Tyr). In addition, the improved characterization of compounds derived from these amino acids could inform strategies for developing crops with greater resilience and improved traits for the biorefinery. Sorghum and other grasses possess phenylalanine ammonia-lyase (PAL) enzymes that generate cinnamic acid from Phe and bifunctional phenylalanine/tyrosine ammonia-lyase (PTAL) enzymes that generate cinnamic acid and p-coumaric acid from Phe and Tyr, respectively. Cinnamic acid can, in turn, be converted into p-coumaric acid by cinnamate 4-hydroxylase. Thus, Phe and Tyr are both precursors of common downstream products. Not all derivatives of Phe and Tyr are shared, however, and each can act as a precursor for unique metabolites. In this study, 13C isotopic-labeled precursors and the recently developed Precursor of Origin Determination in Untargeted Metabolomics (PODIUM) mass spectrometry (MS) analytical pipeline were used to identify over 600 MS features derived from Phe and Tyr in sorghum. These features comprised 20% of the MS signal collected by reverse-phase chromatography and detected through negative-ionization. Ninety percent of the labeled mass features were derived from both Phe and Tyr, although the proportional contribution of each precursor varied. In addition, the relative incorporation of Phe and Tyr varied between metabolites and tissues, suggesting the existence of multiple pools of p-coumaric acid that are fed by the two amino acids. Furthermore, Phe incorporation was greater for many known hydroxycinnamate esters and flavonoid glycosides. In contrast, mass features derived exclusively from Tyr were the most abundant in every tissue. The Phe- and Tyr-derived metabolite library was also utilized to retrospectively annotate soluble MS features in two brown midrib mutants (bmr6 and bmr12) identifying several MS features that change significantly in each mutant.

PARTIAL CHARACTERIZATION OF SOIL HUMIC ACIDS THROUGH BIODEGRADATION

1967 ◽  
Vol 13 (5) ◽  
pp. 581-586 ◽  
Author(s):  
S. P. Mathur ◽  
E. A. Paul
Keyword(s):  
Amino Acids ◽  
Oxygen Tension ◽  
Humic Acids ◽  
Aromatic Amino Acids ◽  
Partial Characterization ◽  
Penicillium Frequentans ◽  
Enzyme Systems ◽  
Culture Filtrates ◽  
Partial Degradation

A strain of Penicillium frequentans was successfully employed for partial degradation and characterization of humic acids. Salicyl alcohol and salicylaldehyde were detected in culture filtrates of the fungus utilizing humates under reduced oxygen tension. The enzyme systems involved in the degradation of humic acids were adaptive. The humate-adapted mycelium was capable of metabolizing a number of compounds which occur in soil as products of degradation of lignin, aromatic amino acids, and plant glycosides but not polyphenolic hydrocarbons, resorcinol, and phloroglucinol.

scholarly journals Characterization of mouse amino acid transporter B0AT1 (slc6a19)

2005 ◽  
Vol 389 (3) ◽  
pp. 745-751 ◽  
Author(s):  
Christoph Böhmer ◽  
Angelika Bröer ◽  
Michael Munzinger ◽  
Sonja Kowalczuk ◽  
John E. J. Rasko ◽  
...  
Keyword(s):  
Amino Acids ◽  
Membrane Potential ◽  
Amino Acid ◽  
Expression System ◽  
Complex Function ◽  
Aromatic Amino Acids ◽  
Inward Currents ◽  
Xenopus Oocyte Expression ◽  
Oocyte Expression System

The mechanism of the mouse (m)B0AT1 (slc6a19) transporter was studied in detail using two electrode voltage-clamp techniques and tracer studies in the Xenopus oocyte expression system. All neutral amino acids induced inward currents at physiological potentials, but large neutral non-aromatic amino acids were the preferred substrates of mB0AT1. Substrates were transported with K0.5 values ranging from approx. 1 mM to approx. 10 mM. The transporter mediates Na+–amino acid co-transport with a stoichiometry of 1:1. No other ions were involved in the transport mechanism. An increase in the extracellular Na+ concentration reduced the K0.5 for leucine, and vice versa. Moreover, the K0.5 values and Vmax values of both substrates varied with the membrane potential. As a result, K0.5 and Vmax values are a complex function of the concentration of substrate and co-substrate and the membrane potential. A model is presented assuming random binding order and a positive charge associated with the ternary [Na+–substrate–transporter] complex, which is consistent with the experimental data.

scholarly journals Isolation and characterization of six human hepatic isometallothioneins

1985 ◽  
Vol 231 (2) ◽  
pp. 375-382 ◽  
Author(s):  
P E Hunziker ◽  
J H R Kägi
Keyword(s):  
Amino Acids ◽  
Aromatic Amino Acids ◽  
Reversed Phase ◽  
Low Ph ◽  
Autopsy Material ◽  
Isolation And Characterization ◽  
Cysteine Content ◽  
Hepatic Metallothionein ◽  
Mammalian Metallothioneins

Human hepatic metallothionein (MT) was separated into six isoforms by using reversed-phase h.p.l.c. at the analytical and preparative levels. By comparison with the h.p.l.c. elution profiles of the charge-separable species MT-1 and MT-2 isolated by the procedure of Bühler & Kägi [(1974) FEBS Lett. 39, 229-234], five of these isoproteins are identified as hitherto unresolved subforms of MT-1, and one is identical with MT-2. The six isoforms have distinct and reproducible retention times at neutral pH, where the metal remains bound to the protein, and at low pH, where the metal is removed. Their amino acid compositions display the high cysteine content and the lack of aromatic amino acids and of histidine typical of mammalian metallothioneins, but they differ significantly with respect to all other amino acids. A survey of autopsy material indicates that in adult human liver all six isoforms are usually expressed, albeit in somewhat variable relative proportions.

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