Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
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Gene/Protein
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Target Concepts:
Gene/Protein
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Query: EC:2.7.1.1 (
hexokinase
)
5,274
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
Nucleoside diphosphokinase
(
NDK
) of human platelets has been purified by chromatography on Blue Sepharose CL-6B gel (purification factor of 950) and shown to be free of adenylate kinase, ATPase and adenylate cyclase. The molecular weight was 70,000 with subunits of 17,000. The pH optimum was 8.0 Km values for ATP and dTDP were determined in two ways using the pyruvate kinase-lactate dehydrogenase coupled enzyme assay. Values of 0.38 and 0.20 mM were obtained for ATP and 0.29 and 0.21 mM for dTDP. Km values for ADP (0.024 mM) and GTP (0.12 mM) were determined with the
hexokinase
-glucose-6-phosphate dehydrogenase coupled enzyme assay. These values are in agreement with those reported for
NDK
from other sources. Theophylline, which inhibits the
NDK
activity of intact platelets and platelet membrane preparations and inhibits the ADP-induced shape change of platelets, was shown to be a competitive inhibitor of both the free and phosphorylated forms of
NDK
with competitive inhibition constants (Kic) of 9.3 and 9.6 mM respectively. Papaverine, another cAMP phosphodiesterase inhibitor, which also inhibits the ADP-induced shape change of platelets, had no inhibitory effect on platelet
NDK
. It was concluded that the inhibitory effect of theophylline on the activity of the purified enzyme was due to the structural similarity between the methylxanthine and the adenine moiety of ADP.
...
PMID:Isolation and kinetic studies of nucleoside diphosphokinase from human platelets and effects of cAMP phosphodiesterase inhibitors. 302 50
1. Lactogenesis was initiated in pregnant rats by ovariectomy, thereby causing progesterone withdrawal, after which the mammary tissue was analysed for contents of enzymes and metabolites concerned with the biosynthesis of lactose. 2. Lactose synthesis increased about 126-fold with little or no accompanying change in the contents of most metabolic intermediates or in the adenine nucleotide energy charge. 3. Comparison of mass-action ratios with equilibrium constants showed that phosphoglucomutase (EC 2.7.5.1), UDP-glucose pyrophosphorylase (EC 2.7.7.9) and UDP-glucose epimerase (EC 5.1.3.2.) catalysed reactions close to equilibrium.
Nucleoside diphosphokinase
(EC 2.7.4.6.) activity was very high and probably equilibrates the UTP-UDP and ATP-ADP couples. Lactose synthetase and
hexokinase
(
EC 2.7.1.1
) appeared to catalyse rate-limiting reactions. 4. Large increases were seen of UDP-glucose pyrophosphorylase (5-fold), lactose synthetase A protein (3.8-fold) and alpha-lactalbumin (28-fold), but not of
hexokinase
, phosphoglucomutase, UDP-glucose epimerase, nucleoside diphosphokinase or glucose 6-phosphate dehydrogenase (EC 1.1.1.49) activities. 5. It appeared that the increased lactose synthesis was largely accounted for by the increased lactose synthetase A protein activity and alpha-lactalbumin.
...
PMID:Progesterone and the metabolic control of the lactose biosynthetic pathway during lactogenesis in the rat. 436 33
