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Investigations on the Regeneration of the Collagen Molecule.

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unique in that pyrophosphate is converted into high energy
phosphoenolpyruvate and made available for ATP synthesis.
In addition it is catalysed by a non-biotin enzyme. The second
reaction (2) is catalysed by oxaloacetic transcarboxylase.
(2) HOOCCHZCOCOOH
+ H3CCHzCOSCoA
fi
H3CCOCOOH 1 H,C--CH(COOH)-COSCoA
Acetyl-CoAor butyrybCoA may be substituted for propionylCoA yielding malonyl-CoA or ethylmalonyl-CoA, respectively. Reaction (2) is unique in that it permits carboxylation
with oxaloacetate and does not involve ATP or C02. The
enzyme involved in reaction (2) contains biotin with a
chemical role (reaction 3) that resembles that found in
certain COz-fixation reactions by Lynen, Knuppe and coworkers.
(3a) Enz-biotin
+ oxaloacetate r?Enz-biotin-COZ + pyruvate
+ propionyl-CoA
Enz-biotin + Methyl-malonyl-CoA
(3b) Enz-biotin-COZ
% -
~ ~ ~ ~ ~ ~ ~ was
b i ~ t ~ Llsing
~ - reaction
i 4 c(3b).
o ~
The
complex obtained was labile but was stabilized by esterification with diazomethane. Subsequent digestion with pronase
yielded radioactive N-methoxycarbonylbiocytin,which was
converted into radioactive N-methoxycarbonylbiotin and
lvsine when hvdrolvsed
with biotinidase. Thus, the biotin in
-~
this transcarboxylase is attached to lysine and serves as a
carboxyl-transferring agent, the COz being linked as carhoxyl
at the 1'-N of the biotin. There was no transfer of the ureido
carbon as proposed by Wakil. The equilibrium of reaction
(3b) favors formation of Enz-biotin-C02. A third enzyme,
methylmalonyl isomerase, has been isolated and catalyses
reaction (4).
COSCoA
(4)
I
H3CCHCOOH ," COSCOA CH~CHZCOOH
The mechanism of reaction (4) was investigated by mass
spectroscopic analysis of the succinyl-CoA formed from an
equal mixture of J ~ C H ~ - C H ( C O O H ) ~ ~ C O S Cand
OA
~ Z C H ~ C H ( C O O H ) ~ ~ C O S CItO A
Has
. shown in this way
that the transfer of COSCoA occurs by a n intramolecular
reaction. The role of these reactions i n propionate formation
is as follows.
HsCCOCOOH
+ H3C -CH(COOH)
COSCoA
HooCCHzCOCooH
HOOCCHzCOCOOH
+
H1CCH2CoSCoA
+ 4 H+HOOCCkr&HzCOOH
+
H ~ C C H ~ C O S C O A HOOCCHzCHzCOOH
H3CCH2C001 I i
HOOCCH~CH~COSCOA
Sum: Pyruvate
r j
r'
HOOCCHZCHZCOSCOA
CH3CH(COSCoA) --COOH
+ 4 H-propionate + H 2 0
Fixation of COz by reaction ( I ) results, in addition, in an
accumulation of succinate.
[GDCh-Ortsverband Miinchen (Germany), Dec. 11 th, 19621
[VB 678/70 IE]
Investigation of Surface Oxides of Carbon
H . P . Roehm, Heidelberg (Germany)
Microcrystalline black carbon in the form of sugar charcoal
was oxidized with 0 2 at about 420 "C. The resulting surface
oxides (or hydroxides in the presence of water) were acidic
and bound mainly to the edges of the hexagonal carbon
layers. It was demonstrated by neutralization with bases of
various strengths (NaHCO3, Na2CO3, NaOH, NaOC2H5)
that the acidic groups had different acidities. Equivalent
amounts of four functions of different acid strengths were
present. It is assumed that these acidic groups are components
of a larger grouping.
Angew. Chem. internut. Edit. / Vol. 2 (1963) / No. 4
The acidic groups were characterized more precisely by
further reactions, e . g . by methylation with diazomethane and
determination of the hydrolyzable methoxyl groups, by
reaction with SOC12, NH3, or dinitrofluorobenzene. The
number of groups reacting was always equivalent to one of
the neutralization values. An attempt was made to allocate
the different acidities into distinct functional groups. It is
assumed that free carboxyl groups, lactones of the fluoroscein
type, and phenolic hydroxyl groups are present.
On treating diamond powder with oxidizing agents, e.g.
sodium hypochlorite, acidic surface oxides were again
obtained, the diamond becoming hydrophilic. Indications of
the presence of carboxyl and tertiary hydroxyl groups were
found. On the other hand, diamond which was treated with
NO2 gas reacted as a base. When diamond powder was
heated to 80OOC at an 0 2 partial pressure of ca. 10-2 mm.
Hg, blackening occured. This discoloration was due to
transformation of diamond into black microcrystalline
carbon on the surface. The presence of small amounts of 0 2 is
necessary for this to occur. The fact that this was black
graphite-like carbon was proved by means of its catalytic
activity in the formation of HBr from its elements.
[Anorganisch-Chemisches Institut der Universitit Heidelberg
(Germany), January 22nd, 19631
[VB 690a/76 IE]
Investigations on the Regeneration of the
Collagen Molecule
K . Kiihn, Heidelberg (Germany)
The collagen molecule is a rod 2800 8, long with a diameter
of 14 8, and consists of three polypeptide chains intertwined
into a three-chain helix. The question investigated is whether a
cell-controlled reaction must be assumed in order to account
for the formation of the complicated collagen structure from
the three 2800 8, polypeptide chains or whether association
of the three chains to form the ordered helix occurs automatically and is governed only by the primary structure of
the protein.
Neutral-salt soluble collagen, which has molecules which do
not exhibit any intramolecular crosslinks, was heated at 38 "C
in a citrate buffer at uH 3.7 for 90 minutes. The molecules
dissociated completely into the three chains. The solution was
subsequently cooled slowly to 4 "C over a period of a week.
Electron-microscopic examination o f the regenerated solution
revealed the rigid rods of the renatured collagen together with
particles which were not present in a rod-like form. By
treating the solution with trypsin, which does not attack
native collagen molecules, any incompletely regenerated
particles were degraded and eliminated. The yield of trypsinresistant collagen was about 50%. The trypsin-resistant
molecules are indistinguishable in their behaviour from
native, non-denaturated collagen. They have the same
temperature of denaturation and form fibrils and longspacing segments identical to those of native collagen.
[Chemisches Institut der Universitit Heidelberg (Germany),
January 22nd, 19631
[VB 690b/78 IE]
Kinetics and Poisoning in Ammonia Synthesis
R . Brill, Berlin-Dahlem (read by H. Schnefer)
Non or singly promoted (AlzO3) catalysts for ammonia
synthesis were poisoned stepwise by small increments of
H2S. These experiments showed that poisoning is a slow
process with a velocity determined by the rate of diffusion
of the poison chemisorbed on the catalyst's surface.
Promoted catalysts can tolerate more poison than nonpromoted ones. The activation energy for the formation of
ammonia is not altered by poisoning in either promoted or
non-promoted catalysts. The poisoning experiments give
excellent confirmation to the rate equations set up by Ozaki,
221
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