Aldo-keto reductase 1B1 and 1B3 (AKR1B1 and AKR1B3) are the pri-mary human and mouse prostaglandin F2a(PGF2a) synthases, respectively,
which catalyze the NADPH-dependent reduction of PGH2, a common
intermediate of various prostanoids, to form PGF2a. In this study, we
found that AKR1B1 and AKR1B3, but not AKR1B7 and AKR1C3, also
catalyzed the isomerization of PGH2 to PGD2 in the absence of NADPH
The catalytic mechanism underlying the aminopeptidase fromStreptomyces
griseus (SGAP) was investigated. pH-dependent activity profiles revealed
the enthalpy of ionization for the hydrolysis of leucine-para-nitroanilide by
SGAP. The value obtained (30 ± 5 kJÆmol
) is typical of a zinc-bound
water molecule, suggesting that the zinc-bound water⁄hydroxide molecule
acts as the reaction nucleophile.
Flavin-dependent thymidylate synthases (FDTS) catalyze the production of
dTMP from dUMP and N
folate). In contrast to human and other classical thymidylate synth-ases, the activity of FDTS depends on a FAD coenzyme, and its catalytic
mechanism is very different.
l-Rhamnose isomerase (l-RhI) catalyzes the reversible isomerization of
l-rhamnose to l-rhamnulose. Pseudomonas stutzeril-RhI, with a broad
substrate specificity, can catalyze not only the isomerization ofl-rhamnose,
but also that betweend-allose andd-psicose. For the aldose–ketose isomer-ization by l-RhI, a metal-mediated hydride-shift mechanism has been
proposed, but the catalytic mechanism is still not entirely understood.
Mechanical engineers typically use mechanics in the design or analysis phases of engineering. If the engineering project were the design of a vehicle, statics might be employed to design the frame of the vehicle, in order to evaluate where the stresses will be most intense. Dynamics might be used when designing the car's engine, to evaluate the forces in the pistons and cams as the engine cycles. Mechanics of materials might be used to choose appropriate materials for the frame and engine. Fluid mechanics might be used to design a ventilation system for the vehicle (see HVAC), or to design...
Although belonging to the widely investigated peroxidase
superfamily, lactoperoxidase (LPO) and myeloperoxidase
(MPO) share structural and functional features that make
them peculiar with respect to other enzymes of the same
group. A survey of the available literature on their catalytic
intermediates enabled us to ask some questions that
remained unanswered. These questions concern controver-sial features of theLPOandMPOcatalytic cycle, suchas the
existence of Compound I and Compound II isomers and
the identification of their spectroscopic properties....
NMR spectroscopy and X-ray crystallography have provi-ded important insight into structural features of phenyl-alanine hydroxylase (PAH) and tyrosine hydroxylase (TH).
Nevertheless, significant problems such as the substrate
specificity of PAHand the different susceptibility of TH
to feedback inhibition by L-3,4-dihydroxyphenylalanine
(L-DOPA) compared with dopamine (DA) remain unre-solved.
We live in the age of biology—the human and many other organisms’
genomes have been sequenced and we are starting to understand the
function of the metabolic machinery responsible for life on our planet.
Thousands of new genes have been discovered, many of these coding for
enzymes of yet unknown function. Understanding the kinetic behavior
of an enzyme provides clues to its possible physiological role. From
a biotechnological point of view, knowledge of the catalytic properties
of an enzyme is required for the design of immobilized enzyme-based
T has ushered in great business
opportunities—and great turmoil. Not since the Industrial
Revolution have the stakes of dealing with change
been so high. Most traditional organizations have
accepted, in theory at least, that they must either change
or die. And even Internet companies such as eBay, Amazon.
com, and America Online recognize that they need
to manage the changes associated with rapid
A reaction happens need the energy to vibrate the molecules and the reactant concentration enough. The energy here is often provided by heat.
However, in living system, high temperature may harm the biological structure
Truly that the concentration in living system is very low. So living organisms solve these problems by using enzyme
Now neutron diffraction is widely applied for the research of crystal, magnetic structure and internal stress of crystalline materials of various classes, including nanocrystalls. In the present book, we make practically short excursion to modern state of neutron diffraction researches of crystal materials of various classes.
Polyamine oxidases are FAD-dependent enzymes catalyzing the oxidation
of polyamines at the secondary amino groups.Zea maysPAO (ZmPAO)
oxidizes the carbon on the endo-side of the N5-nitrogen of spermidine
(Spd) and spermine (Spm).
c-Glutamyltranspeptidase (GGT; EC 220.127.116.11), an enzyme found in organ-isms from bacteria to mammals and plants, plays a central role in glutathi-one metabolism. Structural studies of GGTs from Escherichia coliand
Helicobacter pylori have revealed detailed molecular mechanisms of
catalysis and maturation.
The amino acid sequence of ervatamin-C, a thermostable cysteine protease
from a tropical plant, revealed an additional 24-amino-acid extension at its
C-terminus (CT). The role of this extension peptide in zymogen activation,
catalytic activity, folding and stability of the protease is reported.
The dye-decolorizing peroxidase (DyP)-type peroxidase family is a unique
heme peroxidase family. The primary and tertiary structures of this family
are obviously different from those of other heme peroxidases. However,
the details of the structure–function relationships of this family remain
The structures of copper amine oxidases from various sources show good
similarity, suggesting similar catalytic mechanisms for all members of this
enzyme family. However, the optimal substrates for each member differ,
depending on the source of the enzyme and its location.
Sialylated oligosaccharides, present on mammalian outer-cell surfaces, play
vital roles in cellular interactions and some bacteria are able to mimic these
structures to evade their host’s immune system. It would be of great benefit
to the study of infectious and autoimmune diseases and cancers, to under-stand the pathway of sialylation in detail to enable the design and produc-tion of inhibitors and mimetics.
A family 16 glycoside hydrolase, xyloglucan xyloglucosyl transferase
(EC 18.104.22.168), also known as xyloglucan endotransglycosylase (XET), and
designated isoenzyme HvXET6, was purified approximately 400-fold from
extracts of young barley seedlings.