Die Addition von Imidazolderivaten an DCCI; eine Nebenreaktion bei der Synthese von Histidinpeptiden

Rink, H; Riniker, B.

doi:10.1002/hlca.19740570337

Cited by 33 publications

(6 citation statements)

References 8 publications

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“…Neither EAC-Tyr nor EAC-Cys residues [43,44] seemed to be present, confirming investigations on intact [3H]EACglucoamylase [5]. In contrast, acid hydrolysis released stoichiometric amounts of ethylamine from the histidine-containing fragment Ala274 -Lys279, possibly reflecting that carbodiimide modified the imidazole ring as earlier described by others in both peptide synthesis [45,46] and protein modification experiments [47].…”

Section: Identijkation Of Labelled Amino Acid Residuessupporting

confidence: 77%

Identification of carboxylic acid residues in glucoamylase G2 from Aspergillus niger that participate in catalysis and substrate binding

Svensson

Clarke

Svendesen

et al. 1990

European Journal of Biochemistry

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Functionally important carboxyl groups in glucoamylase G2 from Aspergillus niger were identified using a differential labelling approach which involved modification of the acarbose-inhibited enzyme with 1-ethyl-3-(4-azonia-4,4-dimethylpentyl)carbodiimide (EAC) and inactivation by [3H]EAC following removal of acarbose.Subsequent sequence localization of the substituted acidic residues was facilitated by specific phenylthiohydantoins. The acid cluster Asp176, Glu179 and Glu180 reacted exclusively with [3H]EAC, while Aspl 12, Asp153, Glu259 and Glu389 had incorporated both [3H]EAC and EAC. It is conceivable that one or two of the [3H]EAC-labelled side chains act in catalysis while the other fully protected residue(s) participates in substrate binding probably together with the partially protected ones. Twelve carboxyl groups that reacted with EAC in the enzyme-acarbose complex were also identified.Asp176, Glu179 and Glu180 are all invariant in fungal glucoamylases. Glu180 was tentatively identified as a catalytic group on the basis of sequence alignments to catalytic regions in isomaltase and a-amylase. The partially radiolabelled Aspl 12 corresponds in Taka-amylase A to Tyr75 situated in a substrate binding loop at a distance from the site of cleavage. A possible correlation between carbodiimide modification of an essential carboxyl group and its role in the glucoamylase catalysis is discussed.Fungal glucoamylase (EC 3.2.1.3; 1,4-a-glucan glucohydrolase) has a wide application in the industrial production of glucose syrups from starch [l, 21. Functionally important side chains have previously been localized in the enzyme from Aspergillus niger [3 -71 and have guided regional sequence alignment with different starch-and oligosaccharide-degrading enzymes [8, 91. This insight into structure/function relationships in glucoamylases made it possible to produce purposely altered enzymes by site-directed mutagenesis [lo -121.Catalytic carboxyl groups have been identified in crystallographic studies of a-amylases [8,13] and by affinity labelling in P-amylases [14, 151 and isomaltase [16 -181. These residues appear conserved in a-amylase, maltase, cyclodextrin glucanotransferase, isoamylase, pullulanase and maltogenic a-amylase [9, 19 -221 ; structure predictions of maltase and cyclodextrin glucanotransferases further show they contain an %/&barrel domain [19] like the a-amylases [8, 131. Much less similarity could be recognized, however, with glucoamylase, P-amylase and isomaltase [9]; their catalytic groups had to be experimentally identified. It was decided to apply the differential labelling approach to glucoamylase because it had failed to react with potential affinity labelling reagents (G. Legler and Y. Nitta, personal communications).The catalytic site in glucoamylase is believed to consist of two carboxyl groups [23,24]. In accordance with a commonly accepted mechanism for carbohydrases [8, 13, 16, 25 -271, one of these acts as a general acid, protonating the glucosidic oxygen of the scissile bond, while the other...

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Section: Identijkation Of Labelled Amino Acid Residuessupporting

confidence: 77%

Identification of carboxylic acid residues in glucoamylase G2 from Aspergillus niger that participate in catalysis and substrate binding

Svensson

Clarke

Svendesen

et al. 1990

European Journal of Biochemistry

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“…Scheme VII shows that hydrogenation of 4b gives 7a. 13 Therefore, the same relationship that existed between 3c, 6a, and 6 exists between 4b, 7a, and 7, thus placing the o-hydroxybenzyl substituent in 7 ortho to the methoxyl group. The following sequence of conversions was carried out to provide further evidence for the structure of isouvaretin o-hydroxybenzyl alcohol and boron trifluoride etherate to yield two monomethoxylated, monobenzylated products 11 and 12.…”

Section: Scheme IImentioning

confidence: 94%

“…This was chromatographed over 21 g of silica gel. Elution with 1% ether-benzene gave 95 mg of the tetramethyl ether after crystallization from ethanol: mp 122-124 °C; UV Xmax (MeOH) 326 nm (t 3.93 X 103), 277 (sh, 1.52 X 104), and 272 (1.60 X 104); CD [9]350 +25 400, [9]3i4 -24 500, [9]278 +5240, [9]243sh +2100, [9]230 -2620, [9]216 +18 300; [a]25D +12.8°(c 1.00, benzene); IR (KBr) bands at 1685 and 1595 cm-1; low-resolution mass spectrum m/e (rel abundance) 524 (M+, 100) and 509 (M+ -15,16); NMR (CDC13) 6.70-7.50 (m, 13 H), 5.67 (X of ABX, 1 ), 4.13 (s, 4 H), 3.97 (s, 3 H), 3.82 (s, 3 H), 3.78 (s, 3 H), 3.58 (s, 3 H), and 2.85-3.10 (AB of ABX, 2 H).…”

Section: Experimental Section14mentioning

confidence: 99%

Cytotoxic C-benzylated flavonoids from Uvaria chamae

Lasswell¹,

Hufford²

1977

J. Org. Chem.

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in methanol for 24 h. The filtrate and washes were evaporated to dryness: yield 77 mg, 36% by weight; 127 wmol Val, 7.7 pmol Gly (yield 32%). Total 14C counts recovered in the filtrate indicated a yield of 36%. The solid was recrystallized from ether-petroleum ether. Paper electrophoresis at pH 1.5 gave a single radioactive spot at Rval 0.48 (standards of Gly-Val, Asp, and cyclic Dca-Val appeared at 0.86,0.74, and 0.66, respectively); 'H NMR (Varian HF, 220 MHz, MezSO-de) 6 0.91 (m, 6 H), 1.3-1.4 (broad m, cyclohexyl axial), 1.6-1.8 (broad m, cyclohexyl equatorial), 2.06 (m, 1 H, Val p-CH), 3.1 (m, tertiary CH), 4.1-4.2 (m,3 H, a-CH), 3.8 (~,3H,OCH3),7.32 (d,2H, J=8Hz,cyclohexyl NH), 7.68 (t, 1 H, J = 7 Hz, Gly NH), 8.64 (d, 1 H, J =: 8 Hz, Val XH); I3C NMR (Bruker HX-90, 22.6 MHz, proton decoupled,

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“…Under standard SPPS conditions the two imidazole nitrogens of unprotected His react with electrophiles such N,N 0 -dicyclohexylcarbodiimide [89], catalyze acyltransfer reactions [90], and, above all, promote the racemization of the chiral a-carbon [91].…”

Section: Hismentioning

confidence: 99%

Orthogonal Protecting Groups and Side‐Reactions in Fmoc/tBu Solid‐Phase Peptide Synthesis

Carganico¹,

Papini²

2010

Amino Acids, Peptides and Proteins in Organic Chemistry

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Die Addition von Imidazolderivaten an DCCI; eine Nebenreaktion bei der Synthese von Histidinpeptiden

Cited by 33 publications

References 8 publications

Identification of carboxylic acid residues in glucoamylase G2 from Aspergillus niger that participate in catalysis and substrate binding

Identification of carboxylic acid residues in glucoamylase G2 from Aspergillus niger that participate in catalysis and substrate binding

Cytotoxic C-benzylated flavonoids from Uvaria chamae

Orthogonal Protecting Groups and Side‐Reactions in Fmoc/tBu Solid‐Phase Peptide Synthesis

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