| Summary: | 碩士 === 國防醫學院 === 解剖學研究所 === 83 === The aim of this study was to investigate the biochemical
characters of human platelet thromboxane synthase and the
relationship between thromboxane synthase and the amount of
serum thromboxane A2. Thromboxane A2 (TXA2), a product of
arachidonic acid metabolism in platelets, is a potent platelet-
aggregating inducer and vascular smooth muscle contractor.
Because of its biological properties, TXA2 may be involved in
blood pressure regulation and participate in the
pathophysiology of genetic hypertension. The biosynthesis of
TXA2 is catalyzed by a series of enzymes including
phospholipase A2, prostaglandin H synthase and thromboxane
synthase(TxS).Thromboxane synthase catalyzes the final step of
conversion of prostaglandin H2 to TXA2. The purification and
characterization of TxS from human adult platelets had been
reported. However, the properties of TxS in human fetal
platelets are still unknown. In order to understand the
character of the TxS from human fetal platelets, immunoblotting
experiments and enzyme kinetic assay will be performed. Our
data showed that polyclonal antibody against human platelet TxS
recognized 2 peptides in adult platelet microsomes, whereas the
antiserum recognized only one polypeptide in fetal platelet
microsomes. The enzyme kinetic data showed that the Km values
of Tx-synthase in human adult and fetal platelets were
8.02±1.59 μM and 4.19±0.67 μM respectively. These results
indicate that two isoforms of Tx-synthase may exist in human
platelets.
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