Search results for "proline"
showing 10 items of 183 documents
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 …
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…
Synthesis, structural aspects and bioactivity of the marine cyclopeptide hymenamide C
2001
Abstract Head-to-tail proline containing cyclopeptide hymenamide C [cyclo(Leu-Trp-Pro 3 -Phe-Gly-Pro 6 -Glu); 1 ], isolated from a marine sponge and for which a preliminary immunomodulating activity was reported, was efficiently synthesized by a three-dimensional orthogonal solid-phase strategy (Fmoc/tBu/Allyl) via anchoring the ω -carboxyl function of the glutamic acid to the solid support (PAC–PEG–PS). The linear precursor was entirely assembled and subsequently cyclized on resin, yielding a major product identical to the natural hymenamide C and a minor one, a geometric isomer of hymenamide C ( 2 ), differing for the geometry of peptide linkages at Pro residues. Both the ‘proline-rich’ c…
ChemInform Abstract: Studies on the Biosynthesis of Paraherquamide. Construction of the Amino Acid Framework.
2010
Abstract It has been previously established in this laboratory that the β-methyl-β-hydroxyproline moiety of the potent anthelmintic agent paraherquamide A, is biosynthetically derived from l -isoleucine. The downstream events from l -Ile to paraherquamide A have now been investigated. The synthesis of [1- 13 C]-labeled l -β-methylproline is described by means of a Hoffman–Loeffler–Freytag reaction sequence from [1- 13 C]- l -Ile. This amino acid is shown to be a direct biosynthetic precursor to paraherquamide A by feeding and incorporation experiments in growing cultures of Penicillium fellutanum . Three tryptophan-containing dipeptides of l -β-methylproline have been constructed: [ 13 C 2 …
The 2-oxoglutarate binding site of prolyl 4-hydroxylase. Identification of distinct subsites and evidence for 2-oxoglutarate decarboxylation in a lig…
1984
The structure and function of the 2-oxoglutarate binding site of prolyl 4-hydroxylase was studied by assaying the inhibitory potential of 24 selected aliphatic or aromatic compounds. All except one of them inhibited the enzyme competitively with respect to 2-oxoglutarate and noncompetitively with respect to Fe2+, the Ki values ranging from 0.8 microM to over 15 mM. The Ki values for the two most effective inhibitors, pyridine 2,5-dicarboxylate and 2,4-dicarboxylate, were about 0.8 microM and 2 microM, these compounds being the most potent inhibitors of prolyl 4-hydroxylase with respect to 2-oxoglutarate known so far. Only one of the compounds tested, 2-oxoadipinate, was able to support hydr…
Responses to salt stress in the halophyte Plantago crassifolia (Plantaginaceae)
2004
Abstract General responses to salt stress have been investigated in the halophyte Plantago crassifolia. Seed germination was strongly inhibited by NaCl, although seed viability and germination capacity were not affected by salt pre-treatments. A concentration-dependent inhibition of plant growth was observed in the presence of NaCl, which was accompanied by the accumulation of Na+ ions in the leaves, as determined by cation exchange HPLC. A 20-fold increase of proline content in leaves was observed when plants were treated with 500 m m NaCl, suggesting a protective role against high salinity stress for this amino acid, whose possible mechanism of action is discussed.
Hypusinated eIF5A is required for the translation of collagen.
2021
ABSTRACT Translation of mRNAs that encode peptide sequences with consecutive prolines (polyproline) requires the conserved and essential elongation factor eIF5A to facilitate the formation of peptide bonds. It has been shown that, upon eIF5A depletion, yeast ribosomes stall in polyproline motifs, but also in tripeptide sequences that combine proline with glycine and charged amino acids. Mammalian collagens are enriched in putative eIF5A-dependent Pro-Gly-containing tripeptides. Here, we show that depletion of active eIF5A in mouse fibroblasts reduced collagen type I α1 chain (Col1a1) content, which concentrated around the nuclei. Moreover, it provoked the upregulation of endoplasmic reticul…
Der cytochemische Nachweis von Prolin-Dehydrogenasen, Acetaldehyd-Dehydrogenasen und Dihydrolipons�ure-Dehydrogenase in den Zellen vonSaccharomyces c…
1967
Using the tetrazolium salt Nitro-BT, the following dehydrogenases can be demonstrated cytochemically in the cells ofSaccharomyces cerevisiae: (1)Proline dehydrogenase activity: it cannot be decided whether the formazan production is a result of L-proline: NAD(P)-2-oxidoreductase (E.C. 1.5.1.1) or of L-proline:NAD(P)-5-oxidoreductase(E.C. 1.5.1.2); (2)Aldehyde dehydrogenase activity: using the coenzymes NAD and NADP and the activators KCl and MgCl2, different reaction pictures are obtained which led to the conclusion that aldehyde: NADP oxidoreductase (E.C. 1.2.1.4) and aldehyde: NAD(P) oxidoreductase (E.C. 1.2.1 5) can be demonstrated seperately; (3)Dihydrolipoic dehydrogenase (E.C. 1.6.4.3…
Novel prolinamide-supported polystyrene as highly stereoselective and recyclable organocatalyst for the aldol reaction
2008
A new prolinamide derivative anchored to a polystyrene support has been straightforwardly prepared and employed as heterogeneous catalyst in the direct asymmetric aldol reaction with good results in terms of yield and stereoselectivity. The optimal reaction conditions were found when a 1:2 (v/v) water/chloroform mixture was used. This mixture was the best compromise between the good swelling properties of chloroform and the formation of a concentrated organic phase due to the presence of water. Noticeably, the enantioselectivities obtained employing acetone as ketone were, to the best of our knowledge, the highest achieved with a supported proline derivative. This catalyst can be easily rec…
Polystyrene-supported proline as recyclable catalyst in the Baylis–Hillman reaction of arylaldehydes and methyl or ethyl vinyl ketone
2008
Abstract Polystyrene-supported proline has been used as co-organocatalyst (10 mol%) with imidazole (10 mol%) in the Baylis–Hillman reaction between methyl or ethyl vinyl ketone and arylaldehydes. Recycling studies showed that the proline resin can be used up to five cycles with high isolated yields. This study represents the first example of supported proline as heterogeneous catalyst in the above reaction and broaden the scope of this catalytic material.