The influence of substrates on the interaction of apotrans-ketolase with thiamin diphosphate was investigated in the
presence of magnesium ions. It was shown that the donor
substrates, but not the acceptor substrates, enhance the
affinity of the coenzyme either to only one active center of
transketolase or to both active centers, but to different
degrees in each, resulting in a negative cooperativity for
coenzyme binding. In the absence of donor substrate, neg-ative cooperativity is not observed. ...
Application of polymers from renewable resources - also identified as
biopolymers - has a large potential market due to the current emphasis on
sustainable technology. For optimal R&D achievements and hence benefits
from these market opportunities, it is essential to combine the expertise
available in the vast range of different disciplines in biopolymer science and
Plant family 32 glycoside hydrolase enzymes include hydrolases (cell wall
invertases, fructan exohydrolases, vacuolar invertases) and fructosyltrans-ferases. These enzymes are very similar at the molecular and structural
levels but are functionally different. Understanding the basis of the func-tional diversity in this family is a challenging task.
UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferases (GalNAc
transferases), which initiate mucin-type O-glycan biosynthesis, have broad
acceptor substrate specificities, and it is still unclear how they recognize
peptides with different sequences.
The specificity of the aglycone-binding site ofEscherichia colia-xylosidase
(YicI), which belongs to glycoside hydrolase family 31, was characterized
by examining the enzyme’s transxylosylation-catalyzing property. Acceptor
specificity and regioselectivity were investigated using various sugars as
acceptor substrates anda-xylosyl fluoride as the donor substrate.
Calmodulin (CaM) activates the constitutive isoforms of mammalian nitric
oxide synthase by triggering electron transfer from the reductase domain
FMN to the heme. This enables the enzymes to be regulated by Ca
con-centration. CaM exerts most of its effects on the reductase domain; these
include activation of electron transfer to electron acceptors, and an increase
in the apparent rate of flavin reduction by the substrate NADPH.
Apple flavor is characterized by combinations of ester compounds, which
increase markedly during fruit ripening. The final step in ester biosynthesis
is catalyzed by alcohol acyl transferases (AATs) that use coenzyme A
(CoA) donors together with alcohol acceptors as substrates. The gene
MpAAT1, which produces a predicted protein containing features of other
plant acyl transferases, was isolated fromMalus pumila(cv. Royal Gala).
TheMpAAT1gene is expressed in leaves, flowers and fruit of apple.