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1.
Nagel L Plattner C Budke C Majer Z DeVries AL Berkemeier T Koop T Sewald N 《Amino acids》2011,41(3):719-732
In Arctic and Antarctic marine regions, where the temperature declines below the colligative freezing point of physiological
fluids, efficient biological antifreeze agents are crucial for the survival of polar fish. One group of such agents is classified
as antifreeze glycoproteins (AFGP) that usually consist of a varying number (n = 4–55) of [AAT]
n
-repeating units. The threonine side chain of each unit is glycosidically linked to β-d-galactosyl-(1 → 3)-α-N-acetyl-d-galactosamine. These biopolymers can be considered as biological antifreeze foldamers. A preparative route for stepwise synthesis
of AFGP allows for efficient synthesis. The diglycosylated threonine building block was introduced into the peptide using
microwave-enhanced solid phase synthesis. By this versatile solid phase approach, glycosylated peptides of varying sequences
and lengths could be obtained. Conformational studies of the synthetic AFGP analogs were performed by circular dichroism experiments
(CD). Furthermore, the foldamers were analysed microphysically according to their inhibiting effect on ice recrystallization
and influence on the crystal habit. 相似文献
2.
Carolin Heggemann Carsten Budke Benjamin Schomburg Zsuzsa Majer Marco Wißbrock Thomas Koop Norbert Sewald 《Amino acids》2010,38(1):213-222
Antifreeze glycoproteins enable life at temperatures below the freezing point of physiological solutions. They usually consist
of the repetitive tripeptide unit (-Ala-Ala-Thr-) with the disaccharide α-d-galactosyl-(1–3)-β-N-acetyl-d-galactosamine attached to each hydroxyl group of threonine. Monoglycosylated analogues have been synthesized from the corresponding
monoglycosylated threonine building block by microwave-assisted solid phase peptide synthesis. This method allows the preparation
of analogues containing sequence variations which are not accessible by other synthetic methods. As antifreeze glycoproteins
consist of numerous isoforms they are difficult to obtain in pure form from natural sources. The synthetic peptides have been
structurally analyzed by CD and NMR spectroscopy in proton exchange experiments revealing a structure as flexible as reported
for the native peptides. Microphysical recrystallization tests show an ice structuring influence and ice growth inhibition
depending on the concentration, chain length and sequence of the peptides. 相似文献
3.
Amadori compounds, formed by the Maillard reaction between reducing sugars (e.g., glucose) and amines (e.g., lysine residues
in proteins), are ubiquitous in nature and have been implicated in aging and several chronic diseases. Fructosyl amine oxidases
(FAOXs) are a relatively new class of enzymes that cleave amadori compounds and have been found in fungi, yeast, and bacteria.
This mini-review summarizes over a dozen of FAOXs with different substrate specificities have been isolated, characterized,
and engineered to date. All known FAOX sequences except one have the consensus motif for the ADP-binding βαβ-fold common to
all FAD and NAD enzymes, and a recently solved crystal structure provides important clues for this class of enzymes. FAOXs
have been explored for applications in diabetes diagnosis, detergents, and food processing. Given that naturally occurring
FAOXs can only react directly with small glycated amino acids or short peptides, it is of great interest to engineer and expand
the accessibility of the substrate binding sites of these enzymes. 相似文献
4.
Debasish Haldar Arindam Banerjee 《International journal of peptide research and therapeutics》2006,12(4):341-348
l-Ala modified analogues of amyloid β-peptide residue 17-20 LVFF (-l-Leu-l-Val-l-Phe-l-Phe-) have been designed and synthesized to study their self-assembling propensity, the nature of intermolecular interactions and rationalize with short hydrophobic sequences in the middle of Aβ that have important role in the neuropathology of Alzheimer’s disease. The peptides sequences LVFA and LAFA have been adopted from the β-sheet region of non-amyloidogenic proteins (hemoglobin-like falvoprotein and ATP synthase C chain, respectively). All the reported peptides self-associate into amyloid-like fibrils which are readily stained with a physiological dye Congo red and exhibits green gold birefringence under polarized light. The solid state FTIR studies of the fibrils reveal that the reported peptides self-associate through intermolecular hydrogen bonds to form antiparallel β-sheet structure, which is also supported by molecular modeling studies. This result suggests that l-Ala analogous of Aβ17-20, LVFA and LAFA also have virtually identical aggregation behavior. 相似文献
5.
Modification of protein by carbonyl compounds under in vitro physiological conditions is site-directed. There are few reports
of the site specificity of glycation of proteins using heating conditions of relevance to food processing. The aim of this
study was to determine the site specificity of modification of β-casein (βCN) by glucose and methylglyoxal (MGO). βCN (1.33 M,
3.2%) was heated with either glucose (1.345 M, 4.6%) or MGO (1 mM) at 95°C for up to 4 h. Tryptic digests were prepared and
analysed by ultra performance liquid chromatography electrospray ionisation mass spectrometry (UPLC-ES/MS). The sites of formation
of the Amadori product, N
ε
-(fructosyl)lysine (FL), and the advanced glycation end-products, N
ε
-(carboxymethyl)lysine (CML), MGO-derived dihydroxyimidazolidine (MG-DH) and MGO-derived hydroimidazolone (MG-HI), were located.
FL and CML were detected at K107 and K176 residues in βCN/glucose incubations. Indigenous N
ε
-(lactulosyl)lysine was detected at K107 only. MG-DH and MG-HI were detected at R202 and possibly R183 residues in both βCN/glucose
and βCN/MGO incubations. Glycation of βCN by glucose and MGO resulted in similar site specificity for MG-DH and MG-HI formation. 相似文献
6.
J. Ogawa A. Ryono S. -X. Xie R. M. Vohra R. Indrati H. Miyakawa T. Ueno Y. Ikenaka H. Nanba S. Takahashi S. Shimizu 《Applied microbiology and biotechnology》1999,52(6):797-801
N-Carbamoyl-d-α-amino acid amidohydrolase (d-carbamoylase) was found to distinguish stereochemistry not only at the α-carbon but also at the β-carbon of N-carbamoyl-d-α-amino acids. The enzyme selectively acted on one of the four stereoisomers of N-carbamoyl-α,β-diastereomeric amino acids. This simultaneous recognition of two chiral centers by d-carbamoylase was useful for the fine stereoselective synthesis of α,β-diastereomeric amino acids such as threonine, isoleucine,
3,4-methylenedioxyphenylserine and β-methylphenylalanine. The stereoselectivity for the β-carbon was influenced by the pH
of the reaction mixture and by the bulk of the substituent at the β-carbon.
Received: 18 June 1999 / Received revision: 30 July 1999 / Accepted: 6 August 1999 相似文献
7.
Jun SY Park KM Choi KW Jang MK Kang HY Lee SH Park KH Cha J 《Biotechnology letters》2008,30(4):743-748
To develop a new skin whitening agent, arbutin-β-glycosides were synthesized and evaluated for their melanogenesis inhibitory
activities. Three active compounds were synthesized via the transglycosylation reaction of Thermotoga neapolitana β-glucosidase and purified by recycling preparative HPLC. As compared with arbutin (IC50 = 6 mM), the IC50 values of these compounds were 8, 10, and 5 mM for β-d-glucopyranosyl-(1→6)-arbutin, β-d-glucopyranosyl-(1→4)-arbutin, and β-d-glucopyranosyl-(1→3)-arbutin, respectively. β-d-Glucosyl-(1→3)-arbutin also exerted the most profound inhibitory effects on melanin synthesis in B16F10 melanoma cells. Melanin
synthesis was inhibited to a significant degree at 5 mM, at which concentration the melanin content was reduced to below 70%
of that observed in the untreated cells. Consequently, β-d-glucopyranosyl-(1→3)-arbutin is a more effective depigmentation agent and is also less cytotoxic than the known melanogenesis
inhibitor, arbutin. 相似文献
8.
A nonenzymatic reaction of reducing sugars with the free amino group located at the N terminus of the polypeptide chain or in the lysine side chain results in glycation of proteins. The fragments of glycated proteins obtained by enzymatic hydrolysis could be considered as the biomarkers of both the aging process and diabetes mellitus. Here we propose a new method for the identification of peptide-derived Amadori products in the enzymatic digest of glycated proteins. The products of enzymatic hydrolysis of the model protein ubiquitin were incubated with H218O under microwave activation. We observed that at these conditions the Amadori compounds selectively exchange one oxygen atom in the hexose moiety. The characteristic isotopic pattern of Amadori products treated with H218O allows fast and convenient identification of this group of compounds, whereas nonglycated peptides are not susceptible to isotopic exchange. 相似文献
9.
J. F. Martín 《Applied microbiology and biotechnology》1998,50(1):1-15
Penicillins, cephalosporins and cephamycins are peptide antibiotics synthesized by condensation of l-α-aminoadipic acid, l-cysteine and l-valine to form the tripeptide δ(l-α-aminoadipyl)-l-cysteinyl-d-valine (Aad-Cys-Val) by a non-ribosomal peptide synthetase. The genes pcbAB and pcbC, common to all penicillin and cephalosporin producers, that encode the Aad-Cys-Val synthetase1 and isopenicillin N (IPN) synthase1 respectively, have been cloned and the encoded enzymes studied in detail. The IPN synthase has been crystallized and its
active center identified, providing evidence for the molecular mechanism of cyclization of the tripeptide Aad-Cys-Val to isopenicillin
N. The late genes of the penicillin and cephalosporin pathways have also been characterized although some of the molecular
mechanisms catalyzed by the encoded enzymes (e.g. IPN acyltransferase) are still obscure. In cephamycin-producing organisms,
biosynthesis of the α-aminoadipic acid precursor proceeds in two steps catalyzed by lysine 6-aminotransferase and piperideine-6-carboxylic
acid dehydrogenase. The gene lat for the first of these enzymes is located in the cephamycin gene cluster, providing an interesting example of association
of genes encoding enzymes for the formation of a precursor with genes involved in assembly of the antibiotics. Novel enzymes
involved in methoxylation at C-7 and carbamoylation at C-3′ of the cephem nucleus were isolated from Nocardia lactamdurans and Streptomyces clavuligerus. The methoxylation system is encoded by two linked genes cmcI-cmcJ and their products (proteins P7 and P8) form a complex that is required for hydroxylation at C-7 and for the subsequent methylation of the 7-hydroxycephem derivative
to form the methoxyl group. Carbamoylation at the C-3′-hydroxyl group of the cephem nucleus is catalyzed by a specific carbamoyltransferase
encoded by the gene cmcH. Finally, genes for a β-lactamase (bla), a penicillin-binding protein (pbp) and a transmembrane protein (cmcT) that appears to be involved in cephamycin exportation, are clustered together with the biosynthetic genes in the cephamycin
clusters of S. clavuligerus and N. lactamdurans. Availability of the cloned genes allows metabolic engineering of the β-lactam biosynthetic pathways such as a channelling
precursors and directed removal of bottlenecks in the β-lactam biosynthetic pathways. Several new β-lactam antibiotics have
been discovered in gram-positive and gram-negative bacteria that will provide new genes for combinatorial synthesis of new
molecules.
Received: 2 December 1997 / Received revision: 20 February 1998 / Accepted: 24 February 1998 相似文献
10.
Nina Dückers Katrin Baer Sabine Simon Harald Gröger Werner Hummel 《Applied microbiology and biotechnology》2010,88(2):409-424
Threonine aldolases (TAs) constitute a powerful tool for catalyzing carbon–carbon bond formations in synthetic organic chemistry,
thus enabling an enantio- and diastereoselective synthesis of β-hydroxy-α-amino acids. Starting from the achiral precursors
glycine and an aldehyde, two new stereogenic centres are formed in this catalytic step. The resulting chiral β-hydroxy-α-amino
acid products are important precursors for pharmaceuticals such as thiamphenicol, a l-threo-phenylserine derivative or l-threo-3,4-dihydroxyphenylserine. TAs are pyridoxal-5-phosphate-dependent enzymes, which, in nature, catalyze the cleavage of l-threonine or l-allo-threonine to glycine and acetaldehyde in a glycine biosynthetic pathway. TAs from a broad number of species of bacteria and
fungi have been isolated and characterised as biocatalysts for the synthesis of β-hydroxy-α-amino acids. In this review, screening
methods to obtain novel TAs, their biological function, biochemical characterisation and preparative biotransformations with
TAs are described. 相似文献
11.
Kawai R Igarashi K Yoshida M Kitaoka M Samejima M 《Applied microbiology and biotechnology》2006,71(6):898-906
When Phanerochaete chrysosporium was grown with laminarin (a β-1,3/1,6-glucan) as the sole carbon source, a β-1,3-glucanase with a molecular mass of 36 kDa was produced as a major extracellular protein. The cDNA encoding this enzyme was cloned, and the deduced amino acid sequence revealed that this enzyme belongs to glycoside hydrolase family 16; it was named Lam16A. Recombinant Lam16A, expressed in the methylotrophic yeast Pichia pastoris, randomly hydrolyzes linear β-1,3-glucan, branched β-1,3/1,6-glucan, and β-1,3-1,4-glucan, suggesting that the enzyme is a typical endo-1,3(4)-β-glucanase (EC 3.2.1.6) with broad substrate specificity for β-1,3-glucans. When laminarin and lichenan were used as substrates, Lam16A produced 6-O-glucosyl-laminaritriose (β-d-Glcp-(1–>6)-β-d-Glcp-(1–>3)-β-d-Glcp-(1–>3)-d-Glc) and 4-O-glucosyl-laminaribiose (β-d-Glcp-(1–>4)-β-d-Glcp-(1–>3)-d-Glc), respectively, as one of the major products. These results suggested that the enzyme strictly recognizes β-d-Glcp-(1–>3)-d-Glcp at subsites −2 and −1, whereas it permits 6-O-glucosyl substitution at subsite +1 and a β-1,4-glucosidic linkage at the catalytic site. Consequently, Lam16A generates non-branched oligosaccharide from branched β-1,3/1,6-glucan and, thus, may contribute to the effective degradation of such molecules in combination with other extracellular β-1,3-glucanases. 相似文献
12.
Vassiliki Magafa Lenka Borovičková Jiřina Slaninová Paul Cordopatis 《Amino acids》2010,38(5):1549-1559
We report the solid phase synthesis and some pharmacological properties of 24 oxytocin (OT) analogues. Basic modifications
at position 9 (introduction of l- or d-β-(2-thienyl)-alanine [L- or D-Thi], or l- or d-3-Pyridylalanine [l- or d-3-Pal]) were combined with d-tyrosine(OEthyl) [d-Tyr(Et)] or d-1-naphthylalanine [d-1-Nal] in position 2 and β-mercaptopropionic acid (Mpa) in position 1 modifications in altogether 14 analogues. Additionally, 8 analogues having α-aminoisobutyric acid [Aib] or d-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (d-Tic) or diethylglycine (Deg) in position 9 and d-Tyr(Et) or d-1-Nal or d-Tic in position 2 and Mpa or Pen (ββ-dimethylcysteine) in position 1 were prepared. Two of these analogues have one more modification in position 6, i.e. Pen.
Furthermore, two analogues having Mpa in position 1 and d-Tyr(Et) or d-1-Nal in position 2 were prepared for comparison purposes. The analogues were tested for rat uterotonic activity in vitro,
in the rat pressor assay and for binding affinity to human OT receptor. The analogue having the highest anti-oxytocic activity
was [Mpa1, d-Tyr(Et)2, Deg9]OT (pA2 = 8.68 ± 0.26); this analogue was also selective. 相似文献
13.
Orthogonally protected l-threo-β-ethoxyasparagine (Fmoc-EtOAsn(Trt)-OH, 1) was synthesized from diethyl (2S,3S)-2-azido-3-hydroxysuccinate 2 in eight steps as a building block for solid-phase peptide synthesis. The starting material is easily available in multi-gram
scale from d-diethyltartrate. The transformation steps reported here are robust and scalable. Thus, a significant amount of 1 (1.8 g) was obtained in 21% overall yield. The synthesis reported is also expected to be useful for the preparation of other
O-substituted l-threo-β-hydroxyasparagine derivatives. 相似文献
14.
Proteins have been considered to consist exclusively of l-amino acids in living tissues. However, our previous studies showed that two specific aspartyl (Asp) residues in αA- and
αB-crystallins from human eye lenses invert to the d-isomers to a high degree during aging. The reaction is also accompanied by isomerization into a form containing β-Asp (isoaspartate)
residues. The appearance of d- and β-Asp in a protein potentially induces large changes to the higher order structure of the protein as well as to its
function. However, it remains unclear whether the formation of the Asp isomer is the direct trigger of the change to the higher
order structure and function. In this study, in order to clarify the effect of the inversion to d-isomers in a protein, we synthesized peptides corresponding to the 70–88 (KFVIFLDVKHFSPEDLTVK) fragment of human αA-crystallin
and its corresponding diastereoisomers in which lα-Asp was replaced with lβ-Asp, dα-Asp, and dβ-Asp at position 76 and compared their biochemical properties with that of normal peptide. The peptides containing abnormal
isomers (lβ-Asp, dα-Asp, and dβ-Asp residues, respectively) were more hydrophilic than the normal peptide (containing lα-Asp), lost β-sheet structure and changed to random structures. The normal peptide promoted the aggregation of insulin while
the other three isomers suppressed the aggregation of insulin. This is the first evidence that a single substitution of an
Asp isomer in a peptide induces a large change to the properties of the peptide. 相似文献
15.
Birichevskaya LL Kvach SV Sivets GG Kalinichenko EN Zinchenko AI Mikhailopulo IA 《Biotechnology letters》2007,29(4):585-591
Enzymatic 5′-monophosphorylation and 5′-phosphatidylation of a number of β-l- and β-d-nucleosides was investigated. The first reaction, catalyzed by nucleoside phosphotransferase (NPT) from Erwinia herbicola, consisted of the transfer of the phosphate residue from p-nitrophenylphosphate (p-NPP) to the 5′-hydroxyl group of nucleoside; the second was the phospholipase d (PLD)-catalyzed transphosphatidylation of l-α-lecithin with a series of β-l- and β-d-nucleosides as the phosphatidyl acceptor resulted in the formation of the respective phospholipid-nucleoside conjugates.
Some β-l-nucleosides displayed similar or even higher substrate activity compared to the β-d-enantiomers. 相似文献
16.
Nielsen KA Hrmova M Nielsen JN Forslund K Ebert S Olsen CE Fincher GB Møller BL 《Planta》2006,223(5):1010-1023
Barley (Hordeum vulgare L.) produces a leucine-derived cyanogenic β-d-glucoside, epiheterodendrin that accumulates specifically in leaf epidermis. Barley leaves are not cyanogenic, i.e. they
do not possess the ability to release hydrogen cyanide, because they lack a cyanide releasing β-d-glucosidase. Cyanogenesis was reconstituted in barley leaf epidermal cells through single cell expression of a cDNA encoding
dhurrinase-2, a cyanogenic β-d-glucosidase from sorghum. This resulted in a 35–60% reduction in colonization rate by an obligate parasite Blumeria graminis f. sp. hordei, the causal agent of barley powdery mildew. A database search for barley homologues of dhurrinase-2 identified
a (1,4)-β-d-glucan exohydrolase isozyme βII that is located in the starchy endosperm of barley grain. The purified barley (1,4)-β-d-glucan exohydrolase isozyme βII was found to hydrolyze the cyanogenic β-d-glucosides, epiheterodendrin and dhurrin. Molecular modelling of its active site based on the crystal structure of linamarase
from white clover, demonstrated that the disposition of the catalytic active amino acid residues was structurally conserved.
Epiheterodendrin stimulated appressoria and appressorial hook formation of B. graminis in vitro, suggesting that loss of cyanogenesis in barley leaves has enabled the fungus to utilize the presence of epiheterodendrin
to facilitate host recognition and to establish infection. 相似文献
17.
Fuchs Viola Jaeger Karl-Erich Wilhelm Susanne Rosenau Frank 《World journal of microbiology & biotechnology》2011,27(3):713-718
A gene encoding a so far uncharacterized β-peptidyl aminopeptidase from the opportunistic human pathogen Pseudomonas aeruginosa PAO1 was cloned and actively expressed in the heterologue host Escherichia coli. The gene was identified in the genome sequence by its homology to the S58 family of peptidases. The sequence revealed an
open reading frame of 1,101 bp with a deduced amino acid sequence of 366 amino acids. The gene was amplified by PCR, ligated
into pET22b(+) and was successfully expressed in E. coli BL21 (DE3). It was shown that the enzyme consists of two polypeptides (α- and β-subunit), which are processed from the precursor.
The enzyme is specific for N-terminal β-alanyl dipeptides (β-Ala-Xaa). BapF hydrolyses efficiently β-alanine at the N-terminal
position, including H-β3hAla-pNA, H–D-β3hAla-pNA and β-Ala-l-His (l-carnosine). d- and l-alaninamide were also hydrolysed by the enzyme. 相似文献
18.
Glucose inhibits the inducible synthesis of β-D-glucosidase inStreptomyces granaticolor. Neither cAMP nor cGMP influence the inhibitory effect of glucose. Glucose also inhibits the inducible synthesis of the cellobiose
uptake system but has no effect on its activity. This may be the mechanism underlying glucose inhibition of induction of β-D-glucosidase inS.granaticolor. 相似文献
19.
A bacterium (strain HC1) capable of assimilating rice bran hemicellulose was isolated from a soil and identified as belonging
to the genus Paenibacillus through taxonomical and 16S rDNA sequence analysis. Strain HC1 cells grown on rice bran hemicellulose as a sole carbon source
inducibly produced extracellular xylanase and intracellular glycosidases such as β-d-glucosidase and β-d-arabinosidase. One of them, β-d-glucosidase was further analyzed. A genomic DNA library of the bacterium was constructed in Escherichia coli and gene coding for β-d-glucosidase was cloned by screening for β-d-glucoside-degrading phenotype in E. coli cells. Nucleotide sequence determination indicated that the gene for the enzyme contained an open reading frame consisting
of 1,347 bp coding for a polypeptide with a molecular mass of 51.4 kDa. The polypeptide exhibits significant homology with
other bacterial β-d-glucosidases and belongs to glycoside hydrolase family 1. β-d-Glucosidase purified from E. coli cells was a monomeric enzyme with a molecular mass of 50 kDa most active at around pH 7.0 and 37°C. Strain HC1 glycosidases
responsible for degradation of rice bran hemicellulose are expected to be useful for structurally determining and molecularly
modifying rice bran hemicellulose and its derivatives. 相似文献
20.
The kinetics of β-galactosidase synthesis induced by galactose and lactose inStreptomyces violaceus, as well as the pattern ofo-nitrophenyl-β-d-galactoside-positive bands observed after electrophoresis of both crude extracts, showed the presence of different β-galactosidase
activities in the two cellular extracts. It is postulated that the lactase activity induced by lactose is the physiological
enzyme responsible for lactose utilization. The possible function of the galactose-induced activity is also discussed. 相似文献