The book takes in consideration some dehydrogenases, enzymes with different functions in the cells by using different substrates, such as hydroxysteroid dehydrogenases, aldehyde dehydrogenases, glucose-6-phosphate dehydrogenase, pyruvate dehydrogenase complex, glutamate dehydrogenase, succinate dehydrogenase. They are examined from the following points of view: biochemistry, physiological functions and role in some diseases and in the development of tumours. For these reasons, the book is divided into three sections: 1. Dehydrogenases and cancer 2. Dehydrogenases and some diseases 3.
The pyruvate dehydrogenase complex (PDC) is subjected to
multiple interacting levels of control in plant cells. The first
level is subcellular compartmentation. Plant cells are unique
inhaving twodistinct, spatially separated forms of the PDC;
mitochondrial (mtPDC) and plastidial (plPDC). The
mtPDCis the site of carbon entry into the tricarboxylic acid
cycle, while the plPDCprovides acetyl-CoAandNADHfor
de novofatty acid biosynthesis.
Anumber of cellular systems cooperate in redox regulation,
providing metabolic responses according to changes in the
oxidation (or reduction)of the redox active components of
a cell. Key systems of central metabolism, such as the 2-oxo
acid dehydrogenase complexes, are important participants
in redox regulation, because their function is controlled by
ratio and the complex-bound dihydro-lipoate/lipoate ratio.
Self-regulation of the 2-oxo acid dehydrogenase complexes
during catalysiswas studied.Radical species as sideproducts
of catalysis were detected by spin trapping, lucigenin fluor-escence and ferricytochromec reduction. Studies of the
complexes after converting the bound lipoate or FAD
cofactors tononfunctional derivatives indicated that radicals
are generated viaFAD. In the presence of oxygen, the 2-oxo
acid, CoA-dependent production of the superoxide anion
radical was detected.
Limitedproteolysis of the pyruvate decarboxylase (E1,a2b2
component of the pyruvate dehydrogenase (PDH) multi-enzyme complexofBacillus stearothermophilushas indicated
the importance for catalysis of a site (Tyr281-Arg282) in the
E1asubunit (Chauhan, H.J., Domingo, G.J., Jung, H.-I. &
Perham, R.N. (2000)Eur. J. Biochem.267, 7158–7169).
The pyruvate dehydrogenase complex occupies a central and strategic posi-tion in muscle intermediary metabolism and is primarily regulated by phos-phorylation⁄dephosphorylation. The identification of multiple isoforms of
pyruvate dehydrogenase kinase (PDK1–4) and pyruvate dehydrogenase
phosphatase (PDP1–2) has raised intriguing new possibilities for chronic
pyruvate dehydrogenase complex control.
Two distinguishable activity bands for dye-linkedl-proline dehydrogenase
(PDH1 and PDH2) were detected when crude extract of the hyperthermo-philic archaeonPyrococcus horikoshiiOT-3 was run on a polyacrylamide
gel. After purification, PDH1 was found to be composed of two different
subunits with molecular masses of 56 and 43 kDa, whereas PDH2 was
composed of four different subunits with molecular masses of 52, 46, 20
and 8 kDa.
We report here the first crystal structure of a stable isosteric
analogue of 1,3-bisphospho-D-glyceric acid (1,3-BPGA)
bound to the catalytic domain of Trypanosoma cruzi
glycosomal glyceraldehyde-3-phosphate dehydrogenase
(gGAPDH)in which the two phosphoryl moieties interact
with Arg249. This complex possibly illustrates a step of the
catalytic process by which Arg249 may induce compression
of the product formed, allowing its expulsion fromthe active
Four pyruvate dehydrogenase kinase and two pyruvate
dehydrogenase phosphatase isoforms function in adjusting
the activation state of the pyruvate dehydrogenase complex
(PDC) through determining the fraction of active (non-phosphorylated) pyruvate dehydrogenase component.
Necessary adaptations of PDC activity with varying meta-bolic requirements in different tissues and cell types are met
by the selective expression and pronounced variation in the
inherent functional properties and effector sensitivities of
these regulatory enzymes. ...
Light/dark modulation of the higher plant Calvin-cycle
enzymes phosphoribulokinase (PRK) and NADP-depend-ent glyceraldehyde 3-phosphate dehydrogenase (NADP-GAPDH-A2B2) involves changes of their aggregation state
inaddition to redox changes of regulatory cysteines.Herewe
demonstrate that plants possess two different complexes
containing the inactive forms (a) of NADP-GAPDH and
PRK and (b) of only NADP-GAPDH, respectively, in
Early metabolic steps, including glycolysis and the activity of the pyruvate dehydrogenase complex, yield a two-carbon fragment called an acetyl group, which is linked to a large cofactor known as coenzyme A (or CoA). It is during the citric acid cycle that acetyl-CoA is oxidized to the waste product, carbon dioxide, along with the reduction of the cofactors NAD+ and ubiquinone
The crystal structure of the highly thermostablel-aspartate dehydrogenase
(l-aspDH; EC 220.127.116.11) from the hyperthermophilic archaeon Archaeoglo-bus fulgiduswas determined in the presence of NAD and a substrate ana-log, citrate. The dimeric structure of A. fulgidusl-aspDH was refined at
a resolution of 1.9 A
with a crystallographicR-factor of 21.7% (Rfree ¼
Cloning and over-expression of human glucose 6-phosphate dehydrogenase (Glc6P dehydrogenase) has for the ﬁrst time allowed a detailed kinetic study of a preparation that is genetically homogeneous and in which all the protein molecules are of identical age. The steady-state kinetics of the recombinant enzyme, studied by ﬂuorimetric initial-rate measurements, gave converging linear Lineweaver–Burk plots as expected for a ternary-complex mechanism.
Possible binding proteins of CP12 in a green alga,Chlamydomonas rein-hardtii, were investigated. We covalently immobilized CP12 on a resin and
then used it to trap CP12 partners. Thus, we found an association between
CP12 and phosphoribulokinase (EC 18.104.22.168), glyceraldehyde 3-phosphate
dehydrogenase (EC 22.214.171.124) and aldolase.
NADH dehydrogenase activity was characterized in the mitochondrial
lysates of Phytomonas serpens, a trypanosomatid flagellate parasitizing
plants. Two different high molecular weight NADH dehydrogenases were
characterized by native PAGE and detected by direct in-gel activity stain-ing.
Crystal structures of recombinantLactococcus lactis6-phosphogluconate
dehydrogenase (LlPDH) in complex with substrate, cofactor, product and
inhibitors have been determined. LlPDH shares significant sequence iden-tity with the enzymes from sheep liver and the protozoan parasite Trypano-soma bruceifor which structures have been reported.
he 8.5 kDa chloroplast protein CP12 is essential for assembly of the
phosphoribulokinase⁄glyceraldehyde-3-phosphate dehydrogenase (GAPDH)
complex fromChlamydomonas reinhardtii. After reduction of this complex
with thioredoxin, phosphoribulokinase is released but CP12 remains tightly
associated with GAPDH and downregulates its NADPH-dependent activity.
N-labelled peripheral-subunit binding domain (PSBD) of the dihydro-lipoyl acetyltransferase (E2p) and the dimer of a solubilized interface
domain (E3int) derived from the dihydrolipoyl dehydrogenase (E3) were
used to investigate the basis of the interaction of E2p with E3 in the assem-bly of the pyruvate dehydrogenase multienzyme complex ofBacillus stearo-thermophilus. Thirteen of the 55 amino acids in the PSBD show significant
changes in either or both of the
H amide chemical shifts when
the PSBD forms a 1 : 1 complex with E3int. ...
Acryloyl-CoA reductase fromClostridium propionicum
catalyses the irreversible NADH-dependent formation of
propionyl-CoA from acryloyl-CoA. Purification yielded a
heterohexadecameric yellow–greenish enzyme complex
[(a2bc)4; molecular mass 600 ± 50 kDa] composed of a
propionyl-CoA dehydrogenase (a2,2·40 kDa) and an
electron-transferring flavoprotein (ETF; b,38kDa;c,
29 kDa). A flavin content (90% FAD and 10% FMN) of
2.4 mol pera2bcsubcomplex (149 kDa) was determined.
Pyruvate dehydrogenase kinase (PDK) is the primary
regulator of flux through the mitochondrial pyruvate dehy-drogenase complex (PDC).Analysis of the primary amino-acid sequences of PDK from various sources reveals that
these enzymes include the five domains characteristic of
prokaryotic two-component His-kinases, despite the fact
that PDKexclusivelyphosphorylates Ser residues in theE1a
subunit of the PDC.This seeming contradiction might be
resolved if the PDK-catalyzed reaction employed a phos-pho-His intermediate....