close

Вход

Забыли?

вход по аккаунту

?

Model Reactions for Oxidative Phosphorylation Sulfur Compounds as Carriers of the Phosphoryl Group.

код для вставкиСкачать
acryloyl chloride ; 2) by treatment of optically active amino
esters and tertiary amines with crosslinked chloromethylated polystyrene ; and 3) by polymerization of optically
active acrylic esters and amides.
Resolution was studied in each case with 1-IOmg of
doubly labeled racemic mandelic acid on 10-cm columns.
With almost all the adsorbents enrichment of one antipode
was definitely detectable, at least in the first and last fractions of the eluate. With cinchonine polyacrylate prepared
by method (1) it amounted to IS%, the (R)-(-)-antipode
being enriched in the first fractions. The separation on
ephedrine esters [N-benzylephedrine polyacrylate 30%,
(S)-(+)-antipode eluated first] was even more marked and
could be further improved if the chiral center were built
into a rigid skeleton (Fig. 1).
It is remarkable that the elution profile shows two maxima.
By using longer columns of the synthetic adsorbents it is
now possible for the first time to resolve racemates quantitatively. Further, the second racemate tested by us, namely,
methyl mandelate, is also partly separated into its antipodes
on the adsorbents reported above.
Mercapto and amino groups attached to a protein can
react with CO, to give cyclic carbamic thioesters of type
(3) [51.
If the model compound 11,111, or IV is oxidized with bromine in anhydrous pyridine in presence of A D P and phosphate, then high yields (27-338%) of ATP are obtained by
way of the unisolable, high-energy, phosphorylated compounds such as the quinol phosphate ( 4 ) , the acyl phosphates ( 5 ) , or the carbamoyl phosphates (6).
0
Lecture at Kiel on February 11,1971 [VB 298 IE]
German version: Angew. Chem. 83, 547 (1971)
[l] For a review see G. Lossr and K . Kurirze, 2. Chem. 10, 22 (1970).
[2] Radiochemical and optical purities were proved by isotope dilution
analysis. Reproducible results were also obtained with the test racemate
r3H]-(S)-( +)-mandelic a~id/['~C]-(R)-(
-)-mandelic acid Isotope effects thus did not interfere.
Model Reactions for Oxidative Phosphorylation:
Sulfur Compounds as Carriers of the Phosphoryl
Group
By Edmund Bauerlein and Theodor Wieland"'
For more than ten years T h . Wieland's school have ascribed
particular importance to mercapto groups for transfer of
the
phosphoryl
group"'.
Butyl
thiophosphate,
C,H,S-PO:',
had been synthesized and studied as a
model for a sulfur-containing coenzyme phosphate, CoA
phosphatec2].
Reaction between one member of the electron-transport
chain and the mercapto groups of proteins can lead to p(a1kylthio)phenol (S-alk ylmonothiohydroquinone) (1) [31.
T
-&
6
S'
NH-C-0-P,
(6)
In the same system a new type of reaction was discovered,
namely, direct oxidation of a mercapto compound, specifically mercaptoacetic acidc6](model V, 34% of ATP). The
mixed anhydride (7) of sulfenic and phosphoric acids
must be assumed as the high-energy phosphorylated compound. Lambeth and Lardy[" used a thioether (sulfide),
namely, N-acetylmethionine (model VI) in the same system
(36% of ATP); (8) is presumably the high-energy phosphorylated intermediate.
0 00
II 1
HOOC-CHZ-S-O-P,
HS-CH2-COOH
OB
(7)
Model V
R,?
0
0
IIP-
s-0-P
'oa
R5
(8)
S
Oa
COOH
I
CH-NH- A c
I
CH2-CH2-SCHs
Model VI
SCH3
Red._
0
23QCH3
j$
cH3
OH
OH
(1)
Model I1
Functional groups such as carboxyl and mercapto attached
to the protein may react with each other to give cyclic thioesters of type (2)'"'.
0
SH COOH
(2)
CH3C0-NH720
Model 111
As a model for cytochromes, hemin"' was used successfully
as oxidant of the mercaptoacetic acid (15% of ATP), which
was the most effective of the mercapto compounds tested for
ATP formation[". Thiols are better mediators than H,S
or sulfides.
Our investigations with a lipophilic medium showed that
the yield of ATP obtained on oxidation of mercaptoacetic
acid by hemin is appreciably increasedc9](22% of ATP) by
the presence of its disulfide, dithiobis(acetic acid). Unexpectedly, oxidation of the disulfide alone (in presence of
ADP and phosphate) also led to synthesis ofATP (13.7%);
the thiosulfinate (disulfide monoxide)
F:
[*] Dr. E. Bauerlein and Prof. Dr. Th. Wieland
Max-Planck-Institut fur medizinische Forschung,
Abteilung Chernie
69 Heidelberg, Johnstrasse 29 (Germany)
Angew. Chem. infernat. Edit.
Vol. I0 (1971) No. 7
R-S-S-R
can be assumed to be the first product of this oxidative
phosphor ylation.
52 1
Comparative experiments in an atmosphere of oxygen or
nitrogen showed that there was pronounced oxygendependence of ATP formation in all the hemin experiments
made['01. Thus our results indicate that, rather than the
monomeric cytochrome c, the cytochrome-c oxidase which
probably has quaternary structure is the site of the redox
reaction between mercapto groups and two groups of
hemin compounds (cytochrome a and a3).
Lecture at Dortmund on January 25,1971 [VB 297 IE]
German version: Angew. Chem. 83, 506 (1971)
I
-C-0-R
-C-O-H
-C-
-C-
I
I
+ 2 H,O
Q O C H s
OH
OH
+ 2 HC1
-C-
I
-C-
-C-OH
-C
I
I
113
Tlz. Wieland and E. Biiuerlein, Naturwissenschaften 54, 80 (1967).
[2] Th. Wieland and R. Lambert, Chem. Ber. 89, 2476 (1956).
[3] Th. Wieland and E. Biiuerlein, Monatsh. Chem. 98, 1381 (1967).
[4] Th. Widand and E. Biuerlein, Chem. Ber. IOU, 3869 (1967).
[S] Th. Weland'and H . Aquifa, Chem. Ber. 101, 3031 (1968).
[6] Th. Wieland and E . Bduerlein, Angew. Chem. 80, 915 (1968); Angew. Chem. internat. Edit. 7, 893 (1968).
[7] D. 0.Lambeth and H . A . Lardy, Biochemistry 8, 3395 (1969).
[S] E. BBuerlein and Th. Wieland, Chem. Ber. 103, 648 (1970).
[9] E. Biiuerlein and Th. Wieland, Proceedings of the Colloquium on
Bioenergetics, Bari, Sept. 1970: "Energy transduction in respiration
and photosynthesis".
[lo] E . Biiuerlein, Th. Wiefand,and M . Klinqen&J, J. Europ. Biochem.,
In preparation.
I
I
a
a&
- OH
I
c1
0
0
OH
+CH,OH
+ROH
+2 HC1
R = phenylpropane unit.
Bleaching by chlorine dioxide takes a simiIar course. This
bleaching agent has the advantage that it does not, attack
carbohydrates. Treatment with either chlorine or hypochlorite degrades the carbohydrates (cellulose and hemicelluloses) by oxidation. The keto groups at position 2
and/or 3, or the aldehyde groups at position 6, formed in
the carbohydrate monomers, cause labilization of the p-
The Chemistry of Lignin-removing Bleaching
By Thomas Krause"]
Lignin-removing bleaching of cellulose pulps is usually
carried out in several stages. The bleach sequence consists,
in principle, of a chlorination stage (which leads to partial
degradation of the lignin to alkali-soluble products), alkaline extraction of the degradation products, and one or
several oxidative stages in which hypochlorite and/or
chlorine dioxide is used as bleaching agent. The following
details are extracted from the voluminous literature on
the reactions of lignin and carbohydrates in the individual
bleaching stages :
The chlorination stage leads, when chlorine water (pH = 1.5
to 2.0) is used, to colored o-quinonoid compounds owing
to chlorination of the phenylpropane units of lignin at
positions 5 and 6, followed by hydrolysis of ether linkages
both on the aromatic ring and in the aliphatic side chains.
Further amounts of chlorine are consumed in slow oxidative reactions that probably cause fission of C-C bonds
between the phenylpropane units or removal of aliphatic
side chains. These reactions occur in that way only if the
aromatic ring does not contain other 5- or 6-substituents
and if the phenolic hydroxyl groups are not etherified. The
lignin molecule is cleaved by these reactions into alkalisoluble fragments. The residual lignin in the cellulose pulp
is highly condensed. The subsequent hypochlorite bleaching stage causes only very little chlorination. Oxidations
lead first to o-quinonoid structures; if further favored by
use of higher temperatures, however, they proceed until
the aromatic nucleus is degraded to CO, and organic acids
(e.g., oxalic and maleic acid).
~~
-:
oxidized group;
i
alkali-labile bond.
glucosidic bond to alkali and shortening of the chain by
hydrolytic fission of these bonds in the alkaline medium.
Partial inhibition of carbohydrate degradation can be
achieved by small additions of chlorine dioxide at the
chlorination stage or of sulfamic acid at the hypochlorite
stage.
Lecture at Darmstadt on March 5,1971 [VB 299 IE]
German version: Angew. Chem. 83,548 (1971)
Problems and Results in the Chemistry of Peroxosilicon and Peroxosulfur Compounds
By Armand Blaschette['l
1. Cleavage of benzil and substituted benzils by H,O,,
which is known to depend on nucleophilic attack by HO;
on a carbonyl-carbon atom of the cc-diketone,is specifically
catalyzed by alkali-metal silicates in aqueous solution at
pH>7. Kinetic analysis of the catalyzed reaction, and in
particular the discontinuous pH-dependence of the catalysis constant, shows that the catalytic effect is to be ascribed
to formation of several peroxosilicate species in different
[*] Dr. Th. Krause
Institut fur Makromolekulare Chemie, Lehrstuhl 11.
der Technischen Hochschule
61 Darmstadt, Alexanderstrasse 24 (Germany)
522
[*] Dr. A. Blaschette
Institut fur Anorganische Chemie der Technischen Universitat
33 Braunschweig, Pockelsstrasse 4 (Germany)
Angew. Chem. internat. Edit.
Vol. 10 (1971)
No. 7
Документ
Категория
Без категории
Просмотров
2
Размер файла
207 Кб
Теги
carrier, phosphorylation, mode, reaction, compounds, group, oxidative, sulfur, phosphorus
1/--страниц
Пожаловаться на содержимое документа