Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P00750 (PLA)
 16,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Human pregnancy zone protein (PZP) is a major pregnancy-associated plasma protein strongly related to alpha2-macroglobulin (alpha2-M). Interactions of tissue plasminogen activator (t-PA) with PZP and alpha2-M were both investigated in vitro and the complexes were analyzed by polyacrylamide gel electrophoresis (PAGE). The results demonstrated that PZP-t-PA complex formation was evident within 1 h of incubation, whereas alpha2-M-t-PA complexes were formed after 18 h. Conclusions were supported by the following evidence: (i) PZP and alpha2-M complexes revealed changes of the mobility rate in non-denaturing PAGE, similar to those observed with alpha-Ms-chymotrypsin; (ii) both PZP and alpha2-M formed complexes of molecular size >360 kDa by SDS-PAGE, in accordance with the covalent binding of t-PA, which was previously reported for other proteinases; and (iii) PZP underwent a specific cleavage of the bait region with appearence of fragments of 85-90 kDa as judged by reducing SDS-PAGE. In contrast, the proteolytic attack on alpha2-M was found to occur more slowly, requiring several hours of incubation with t-PA for generation of an appreciable amount of fragments of 85-90 kDa. The appearance of free SH-groups of alpha-Ms was further investigated by titration with 5, 5'-dithiobis(2-nitrobenzoic acid). The maximal level of SH-groups raised was 3.9 mol/mol of PZP and 3.5 mol/mol of alpha2-M, indicating approximately one SH-group for each 180-kDa subunit. Finally, t-PA activity in PZP-t-PA complex was evaluated by measuring the hydrolysis of the chromogenic substrate Flavigen t-PA. Our results revealed that prolongation of the incubation period of this complex increased t-PA-mediated hydrolysis of Flavigen t-PA until a plateau was reached, approximately between 60 and 120 min. The present study suggests that PZP, by binding to t-PA, may contribute to the control of the activity of proteinases derived from fibrinolytic systems.
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PMID:Interaction of human tissue plasminogen activator (t-PA) with pregnancy zone protein: a comparative study with t-PA-alpha2-macroglobulin interaction. 968 14

Tissue-type plasminogen activator (t-PA), is a serine proteinase that catalyzes the initial and rate-limiting step in the fibrinolytic cascade. Its plasma activity is determined by the rate of release into the bloodstream, the rate of inhibition by plasminogen-activator inhibitor type 1 (PAI-1) and the rate of hepatic clearance. Two receptor systems contribute to the clearance of t-PA: the mannose receptor and the low-density lipoprotein receptor-related protein (LRP) that removes free t-PA as well as t-PA-PAI-1 complexes from the blood. During pregnancy a significant rise in the plasma levels of pregnancy zone protein (PZP) is observed, while alpha(2)-macroglobulin (alpha(2)-M) remains constant. Interestingly, the fibrinolytic activity is decreased during this period. In this context, we have recently demonstrated the in vitro formation of PZP-t-PA complexes. Here, we purified LRP from human placenta by affinity chromatography and then analyzed the binding specificity and affinity of PZP-proteinase complexes to the receptor by enzyme immunoassay (EIA). Our results clearly established that the binding of PZP-t-PA complexes to LRP was specific, saturable, and with K(d) = 337 +/- 31 nM. Moreover, by using the same EIA, we further observed that this binding was inhibited by receptor-associated protein. These data suggest that PZP, by binding to t-PA and promoting its clearance via LRP, might contribute in vivo to the downregulation of the fibrinolytic activity during pregnancy.
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PMID:Pregnancy zone protein-tissue-type plasminogen activator complexes bind to low-density lipoprotein receptor-related protein (LRP). 1133 11